| Message ID | 20210827191858.2037087-3-surenb@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Anonymous VMA naming patches | expand |
On Fri, Aug 27, 2021 at 12:18:57PM -0700, Suren Baghdasaryan wrote: > + anon_name = vma_anon_name(vma); > + if (anon_name) { > + seq_pad(m, ' '); > + seq_puts(m, "[anon:"); > + seq_write(m, anon_name, strlen(anon_name)); > + seq_putc(m, ']'); > + } ... > + case PR_SET_VMA_ANON_NAME: > + name = strndup_user((const char __user *)arg, > + ANON_VMA_NAME_MAX_LEN); > + > + if (IS_ERR(name)) > + return PTR_ERR(name); > + > + for (pch = name; *pch != '\0'; pch++) { > + if (!isprint(*pch)) { > + kfree(name); > + return -EINVAL; I think isprint() is too weak a check. For example, I would suggest forbidding the following characters: ':', ']', '[', ' '. Perhaps isalnum() would be better? (permit a-zA-Z0-9) I wouldn't necessarily be opposed to some punctuation characters, but let's avoid creating confusion. Do you happen to know which characters are actually in use today?
On Sat, Aug 28, 2021 at 02:47:03AM +0100, Matthew Wilcox wrote: > On Fri, Aug 27, 2021 at 12:18:57PM -0700, Suren Baghdasaryan wrote: > > + anon_name = vma_anon_name(vma); > > + if (anon_name) { > > + seq_pad(m, ' '); > > + seq_puts(m, "[anon:"); > > + seq_write(m, anon_name, strlen(anon_name)); > > + seq_putc(m, ']'); > > + } Maybe after seq_pad, use: seq_printf(m, "[anon:%s]", anon_name); > > ... > > > + case PR_SET_VMA_ANON_NAME: > > + name = strndup_user((const char __user *)arg, > > + ANON_VMA_NAME_MAX_LEN); > > + > > + if (IS_ERR(name)) > > + return PTR_ERR(name); > > + > > + for (pch = name; *pch != '\0'; pch++) { > > + if (!isprint(*pch)) { > > + kfree(name); > > + return -EINVAL; > > I think isprint() is too weak a check. For example, I would suggest > forbidding the following characters: ':', ']', '[', ' '. Perhaps > isalnum() would be better? (permit a-zA-Z0-9) I wouldn't necessarily > be opposed to some punctuation characters, but let's avoid creating > confusion. Do you happen to know which characters are actually in use > today? There's some sense in refusing [, ], and :, but removing " " seems unhelpful for reasonable descriptors. As long as weird stuff is escaped, I think it's fine. Any parser can just extract with m|\[anon:(.*)\]$| For example, just escape it here instead of refusing to take it. Something like: name = strndup_user((const char __user *)arg, ANON_VMA_NAME_MAX_LEN); escaped = kasprintf(GFP_KERNEL, "%pE", name); if (escaped) { kfree(name); return -ENOMEM; } kfree(name); name = escaped;
On Fri, Aug 27, 2021 at 12:18:57PM -0700, Suren Baghdasaryan wrote: > > The name is stored in a pointer in the shared union in vm_area_struct > that points to a null terminated string. Anonymous vmas with the same > name (equivalent strings) and are otherwise mergeable will be merged. > The name pointers are not shared between vmas even if they contain the > same name. The name pointer is stored in a union with fields that are > only used on file-backed mappings, so it does not increase memory usage. > > The patch is based on the original patch developed by Colin Cross, more > specifically on its latest version [1] posted upstream by Sumit Semwal. > It used a userspace pointer to store vma names. In that design, name > pointers could be shared between vmas. However during the last upstreaming > attempt, Kees Cook raised concerns [2] about this approach and suggested > to copy the name into kernel memory space, perform validity checks [3] > and store as a string referenced from vm_area_struct. > One big concern is about fork() performance which would need to strdup > anonymous vma names. Dave Hansen suggested experimenting with worst-case > scenario of forking a process with 64k vmas having longest possible names > [4]. I ran this experiment on an ARM64 Android device and recorded a > worst-case regression of almost 40% when forking such a process. This > regression is addressed in the followup patch which replaces the pointer > to a name with a refcounted structure that allows sharing the name pointer > between vmas of the same name. Instead of duplicating the string during > fork() or when splitting a vma it increments the refcount. > > [1] https://lore.kernel.org/linux-mm/20200901161459.11772-4-sumit.semwal@linaro.org/ > [2] https://lore.kernel.org/linux-mm/202009031031.D32EF57ED@keescook/ > [3] https://lore.kernel.org/linux-mm/202009031022.3834F692@keescook/ > [4] https://lore.kernel.org/linux-mm/5d0358ab-8c47-2f5f-8e43-23b89d6a8e95@intel.com/ ... > + > +/* mmap_lock should be read-locked */ > +static inline bool is_same_vma_anon_name(struct vm_area_struct *vma, > + const char *name) > +{ > + const char *vma_name = vma_anon_name(vma); > + > + if (likely(!vma_name)) > + return name == NULL; > + > + return name && !strcmp(name, vma_name); > +} Hi Suren! There is very important moment with this new feature: if we assign a name to some VMA it won't longer be mergeable even if near VMA matches by all other attributes such as flags, permissions and etc. I mean our vma_merge() start considering the vma namings and names mismatch potentially blocks merging which happens now without this new feature. Is it known behaviour or I miss something pretty obvious here?
On Fri, Aug 27, 2021 at 10:52 PM Kees Cook <keescook@chromium.org> wrote: > > On Sat, Aug 28, 2021 at 02:47:03AM +0100, Matthew Wilcox wrote: > > On Fri, Aug 27, 2021 at 12:18:57PM -0700, Suren Baghdasaryan wrote: > > > + anon_name = vma_anon_name(vma); > > > + if (anon_name) { > > > + seq_pad(m, ' '); > > > + seq_puts(m, "[anon:"); > > > + seq_write(m, anon_name, strlen(anon_name)); > > > + seq_putc(m, ']'); > > > + } > > Maybe after seq_pad, use: seq_printf(m, "[anon:%s]", anon_name); Good idea. Will change. > > > > > ... > > > > > + case PR_SET_VMA_ANON_NAME: > > > + name = strndup_user((const char __user *)arg, > > > + ANON_VMA_NAME_MAX_LEN); > > > + > > > + if (IS_ERR(name)) > > > + return PTR_ERR(name); > > > + > > > + for (pch = name; *pch != '\0'; pch++) { > > > + if (!isprint(*pch)) { > > > + kfree(name); > > > + return -EINVAL; > > > > I think isprint() is too weak a check. For example, I would suggest > > forbidding the following characters: ':', ']', '[', ' '. Perhaps > > isalnum() would be better? (permit a-zA-Z0-9) I wouldn't necessarily > > be opposed to some punctuation characters, but let's avoid creating > > confusion. Do you happen to know which characters are actually in use > > today? > > There's some sense in refusing [, ], and :, but removing " " seems > unhelpful for reasonable descriptors. As long as weird stuff is escaped, > I think it's fine. Any parser can just extract with m|\[anon:(.*)\]$| I see no issue in forbidding '[' and ']' but whitespace and ':' are currently used by Android. Would forbidding or escaping '[' and ']' be enough? > > For example, just escape it here instead of refusing to take it. Something > like: > > name = strndup_user((const char __user *)arg, > ANON_VMA_NAME_MAX_LEN); > escaped = kasprintf(GFP_KERNEL, "%pE", name); Did you mean "%*pE" as in https://www.kernel.org/doc/html/latest/core-api/printk-formats.html#raw-buffer-as-an-escaped-string ? > if (escaped) { > kfree(name); > return -ENOMEM; > } > kfree(name); > name = escaped; > > -- > Kees Cook
On Sat, Aug 28, 2021 at 2:28 PM Cyrill Gorcunov <gorcunov@gmail.com> wrote: > > On Fri, Aug 27, 2021 at 12:18:57PM -0700, Suren Baghdasaryan wrote: > > > > The name is stored in a pointer in the shared union in vm_area_struct > > that points to a null terminated string. Anonymous vmas with the same > > name (equivalent strings) and are otherwise mergeable will be merged. > > The name pointers are not shared between vmas even if they contain the > > same name. The name pointer is stored in a union with fields that are > > only used on file-backed mappings, so it does not increase memory usage. > > > > The patch is based on the original patch developed by Colin Cross, more > > specifically on its latest version [1] posted upstream by Sumit Semwal. > > It used a userspace pointer to store vma names. In that design, name > > pointers could be shared between vmas. However during the last upstreaming > > attempt, Kees Cook raised concerns [2] about this approach and suggested > > to copy the name into kernel memory space, perform validity checks [3] > > and store as a string referenced from vm_area_struct. > > One big concern is about fork() performance which would need to strdup > > anonymous vma names. Dave Hansen suggested experimenting with worst-case > > scenario of forking a process with 64k vmas having longest possible names > > [4]. I ran this experiment on an ARM64 Android device and recorded a > > worst-case regression of almost 40% when forking such a process. This > > regression is addressed in the followup patch which replaces the pointer > > to a name with a refcounted structure that allows sharing the name pointer > > between vmas of the same name. Instead of duplicating the string during > > fork() or when splitting a vma it increments the refcount. > > > > [1] https://lore.kernel.org/linux-mm/20200901161459.11772-4-sumit.semwal@linaro.org/ > > [2] https://lore.kernel.org/linux-mm/202009031031.D32EF57ED@keescook/ > > [3] https://lore.kernel.org/linux-mm/202009031022.3834F692@keescook/ > > [4] https://lore.kernel.org/linux-mm/5d0358ab-8c47-2f5f-8e43-23b89d6a8e95@intel.com/ > ... > > + > > +/* mmap_lock should be read-locked */ > > +static inline bool is_same_vma_anon_name(struct vm_area_struct *vma, > > + const char *name) > > +{ > > + const char *vma_name = vma_anon_name(vma); > > + > > + if (likely(!vma_name)) > > + return name == NULL; > > + > > + return name && !strcmp(name, vma_name); > > +} > > Hi Suren! There is very important moment with this new feature: if > we assign a name to some VMA it won't longer be mergeable even if > near VMA matches by all other attributes such as flags, permissions > and etc. I mean our vma_merge() start considering the vma namings > and names mismatch potentially blocks merging which happens now > without this new feature. Is it known behaviour or I miss something > pretty obvious here? Hi Cyrill, Correct, this is a known drawback of naming an anonymous VMA. I think I'll need to document this in prctl(2) manpage, which I should update to include this new PR_SET_VMA_ANON_NAME option. Thanks for pointing it out! Suren.
On 28/08/2021 23.47, Suren Baghdasaryan wrote: > On Fri, Aug 27, 2021 at 10:52 PM Kees Cook <keescook@chromium.org> wrote: >> >>>> + case PR_SET_VMA_ANON_NAME: >>>> + name = strndup_user((const char __user *)arg, >>>> + ANON_VMA_NAME_MAX_LEN); >>>> + >>>> + if (IS_ERR(name)) >>>> + return PTR_ERR(name); >>>> + >>>> + for (pch = name; *pch != '\0'; pch++) { >>>> + if (!isprint(*pch)) { >>>> + kfree(name); >>>> + return -EINVAL; >>> >>> I think isprint() is too weak a check. For example, I would suggest >>> forbidding the following characters: ':', ']', '[', ' '. Perhaps Indeed. There's also the issue that the kernel's ctype actually implements some almost-but-not-quite latin1, so (some) chars above 0x7f would also pass isprint() - while everybody today expects utf-8, so the ability to put almost arbitrary sequences of chars with the high bit set could certainly confuse some parsers. IOW, don't use isprint() at all, just explicitly check for the byte values that we and up agreeing to allow/forbid. >>> isalnum() would be better? (permit a-zA-Z0-9) I wouldn't necessarily >>> be opposed to some punctuation characters, but let's avoid creating >>> confusion. Do you happen to know which characters are actually in use >>> today? >> >> There's some sense in refusing [, ], and :, but removing " " seems >> unhelpful for reasonable descriptors. As long as weird stuff is escaped, >> I think it's fine. Any parser can just extract with m|\[anon:(.*)\]$| > > I see no issue in forbidding '[' and ']' but whitespace and ':' are > currently used by Android. Would forbidding or escaping '[' and ']' be > enough? how about allowing [0x20, 0x7e] except [0x5b, 0x5d], i.e. all printable (including space) ascii characters, except [ \ ] - the brackets as already discussed, and backslash because then there's nobody who can get confused about whether there's some (and then which?) escaping mechanism in play - "\n" is simply never going to appear. Simple rules, easy to implement, easy to explain in a man page. >> >> For example, just escape it here instead of refusing to take it. Something >> like: >> >> name = strndup_user((const char __user *)arg, >> ANON_VMA_NAME_MAX_LEN); >> escaped = kasprintf(GFP_KERNEL, "%pE", name); I would not go down that road. First, it makes it much harder to explain the rules for what are allowed and not allowed. Second, parsers become much more complicated. Third, does the length limit then apply to the escaped or unescaped string? Rasmus
On Mon, Aug 30, 2021 at 1:12 AM Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote: > > On 28/08/2021 23.47, Suren Baghdasaryan wrote: > > On Fri, Aug 27, 2021 at 10:52 PM Kees Cook <keescook@chromium.org> wrote: > >> > >>>> + case PR_SET_VMA_ANON_NAME: > >>>> + name = strndup_user((const char __user *)arg, > >>>> + ANON_VMA_NAME_MAX_LEN); > >>>> + > >>>> + if (IS_ERR(name)) > >>>> + return PTR_ERR(name); > >>>> + > >>>> + for (pch = name; *pch != '\0'; pch++) { > >>>> + if (!isprint(*pch)) { > >>>> + kfree(name); > >>>> + return -EINVAL; > >>> > >>> I think isprint() is too weak a check. For example, I would suggest > >>> forbidding the following characters: ':', ']', '[', ' '. Perhaps > > Indeed. There's also the issue that the kernel's ctype actually > implements some almost-but-not-quite latin1, so (some) chars above 0x7f > would also pass isprint() - while everybody today expects utf-8, so the > ability to put almost arbitrary sequences of chars with the high bit set > could certainly confuse some parsers. IOW, don't use isprint() at all, > just explicitly check for the byte values that we and up agreeing to > allow/forbid. > > >>> isalnum() would be better? (permit a-zA-Z0-9) I wouldn't necessarily > >>> be opposed to some punctuation characters, but let's avoid creating > >>> confusion. Do you happen to know which characters are actually in use > >>> today? > >> > >> There's some sense in refusing [, ], and :, but removing " " seems > >> unhelpful for reasonable descriptors. As long as weird stuff is escaped, > >> I think it's fine. Any parser can just extract with m|\[anon:(.*)\]$| > > > > I see no issue in forbidding '[' and ']' but whitespace and ':' are > > currently used by Android. Would forbidding or escaping '[' and ']' be > > enough? > > how about allowing [0x20, 0x7e] except [0x5b, 0x5d], i.e. all printable > (including space) ascii characters, except [ \ ] - the brackets as > already discussed, and backslash because then there's nobody who can get > confused about whether there's some (and then which?) escaping mechanism > in play - "\n" is simply never going to appear. Simple rules, easy to > implement, easy to explain in a man page. Thanks for the suggestion, Rasmus. I'm all for keeping it simple. Kees, Matthew, would that be acceptable? > > >> > >> For example, just escape it here instead of refusing to take it. Something > >> like: > >> > >> name = strndup_user((const char __user *)arg, > >> ANON_VMA_NAME_MAX_LEN); > >> escaped = kasprintf(GFP_KERNEL, "%pE", name); > > I would not go down that road. First, it makes it much harder to explain > the rules for what are allowed and not allowed. Second, parsers become > much more complicated. Third, does the length limit then apply to the > escaped or unescaped string? > > Rasmus
On Mon, Aug 30, 2021 at 09:16:14AM -0700, Suren Baghdasaryan wrote: > On Mon, Aug 30, 2021 at 1:12 AM Rasmus Villemoes > <linux@rasmusvillemoes.dk> wrote: > > > > On 28/08/2021 23.47, Suren Baghdasaryan wrote: > > > On Fri, Aug 27, 2021 at 10:52 PM Kees Cook <keescook@chromium.org> wrote: > > >> > > >>>> + case PR_SET_VMA_ANON_NAME: > > >>>> + name = strndup_user((const char __user *)arg, > > >>>> + ANON_VMA_NAME_MAX_LEN); > > >>>> + > > >>>> + if (IS_ERR(name)) > > >>>> + return PTR_ERR(name); > > >>>> + > > >>>> + for (pch = name; *pch != '\0'; pch++) { > > >>>> + if (!isprint(*pch)) { > > >>>> + kfree(name); > > >>>> + return -EINVAL; > > >>> > > >>> I think isprint() is too weak a check. For example, I would suggest > > >>> forbidding the following characters: ':', ']', '[', ' '. Perhaps > > > > Indeed. There's also the issue that the kernel's ctype actually > > implements some almost-but-not-quite latin1, so (some) chars above 0x7f > > would also pass isprint() - while everybody today expects utf-8, so the > > ability to put almost arbitrary sequences of chars with the high bit set > > could certainly confuse some parsers. IOW, don't use isprint() at all, > > just explicitly check for the byte values that we and up agreeing to > > allow/forbid. > > > > >>> isalnum() would be better? (permit a-zA-Z0-9) I wouldn't necessarily > > >>> be opposed to some punctuation characters, but let's avoid creating > > >>> confusion. Do you happen to know which characters are actually in use > > >>> today? > > >> > > >> There's some sense in refusing [, ], and :, but removing " " seems > > >> unhelpful for reasonable descriptors. As long as weird stuff is escaped, > > >> I think it's fine. Any parser can just extract with m|\[anon:(.*)\]$| > > > > > > I see no issue in forbidding '[' and ']' but whitespace and ':' are > > > currently used by Android. Would forbidding or escaping '[' and ']' be > > > enough? > > > > how about allowing [0x20, 0x7e] except [0x5b, 0x5d], i.e. all printable > > (including space) ascii characters, except [ \ ] - the brackets as > > already discussed, and backslash because then there's nobody who can get > > confused about whether there's some (and then which?) escaping mechanism > > in play - "\n" is simply never going to appear. Simple rules, easy to > > implement, easy to explain in a man page. > > Thanks for the suggestion, Rasmus. I'm all for keeping it simple. > Kees, Matthew, would that be acceptable? Yes, I think so. It permits all kinds of characters that might be confusing if passed on to something else, but we can't prohibit everything, and forbidding just these three should remove any confusion for any parser of /proc. Little Bobby Tables thanks you.
On Mon, Aug 30, 2021 at 9:59 AM Matthew Wilcox <willy@infradead.org> wrote: > > On Mon, Aug 30, 2021 at 09:16:14AM -0700, Suren Baghdasaryan wrote: > > On Mon, Aug 30, 2021 at 1:12 AM Rasmus Villemoes > > <linux@rasmusvillemoes.dk> wrote: > > > > > > On 28/08/2021 23.47, Suren Baghdasaryan wrote: > > > > On Fri, Aug 27, 2021 at 10:52 PM Kees Cook <keescook@chromium.org> wrote: > > > >> > > > >>>> + case PR_SET_VMA_ANON_NAME: > > > >>>> + name = strndup_user((const char __user *)arg, > > > >>>> + ANON_VMA_NAME_MAX_LEN); > > > >>>> + > > > >>>> + if (IS_ERR(name)) > > > >>>> + return PTR_ERR(name); > > > >>>> + > > > >>>> + for (pch = name; *pch != '\0'; pch++) { > > > >>>> + if (!isprint(*pch)) { > > > >>>> + kfree(name); > > > >>>> + return -EINVAL; > > > >>> > > > >>> I think isprint() is too weak a check. For example, I would suggest > > > >>> forbidding the following characters: ':', ']', '[', ' '. Perhaps > > > > > > Indeed. There's also the issue that the kernel's ctype actually > > > implements some almost-but-not-quite latin1, so (some) chars above 0x7f > > > would also pass isprint() - while everybody today expects utf-8, so the > > > ability to put almost arbitrary sequences of chars with the high bit set > > > could certainly confuse some parsers. IOW, don't use isprint() at all, > > > just explicitly check for the byte values that we and up agreeing to > > > allow/forbid. > > > > > > >>> isalnum() would be better? (permit a-zA-Z0-9) I wouldn't necessarily > > > >>> be opposed to some punctuation characters, but let's avoid creating > > > >>> confusion. Do you happen to know which characters are actually in use > > > >>> today? > > > >> > > > >> There's some sense in refusing [, ], and :, but removing " " seems > > > >> unhelpful for reasonable descriptors. As long as weird stuff is escaped, > > > >> I think it's fine. Any parser can just extract with m|\[anon:(.*)\]$| > > > > > > > > I see no issue in forbidding '[' and ']' but whitespace and ':' are > > > > currently used by Android. Would forbidding or escaping '[' and ']' be > > > > enough? > > > > > > how about allowing [0x20, 0x7e] except [0x5b, 0x5d], i.e. all printable > > > (including space) ascii characters, except [ \ ] - the brackets as > > > already discussed, and backslash because then there's nobody who can get > > > confused about whether there's some (and then which?) escaping mechanism > > > in play - "\n" is simply never going to appear. Simple rules, easy to > > > implement, easy to explain in a man page. > > > > Thanks for the suggestion, Rasmus. I'm all for keeping it simple. > > Kees, Matthew, would that be acceptable? > > Yes, I think so. It permits all kinds of characters that might > be confusing if passed on to something else, but we can't prohibit > everything, and forbidding just these three should remove any confusion > for any parser of /proc. Little Bobby Tables thanks you. Thanks for all the feedback! I think I have enough change suggestions to resping the next revision. Will send an update later today.
On Fri 27-08-21 12:18:57, Suren Baghdasaryan wrote: [...] > Userspace can set the name for a region of memory by calling > prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, start, len, (unsigned long)name); > Setting the name to NULL clears it. Maybe I am missing this part but I do not see this being handled anywhere. [...] > @@ -3283,5 +3283,16 @@ static inline int seal_check_future_write(int seals, struct vm_area_struct *vma) > return 0; > } > > +#ifdef CONFIG_ADVISE_SYSCALLS > +int madvise_set_anon_name(struct mm_struct *mm, unsigned long start, > + unsigned long len_in, const char *name); > +#else > +static inline int > +madvise_set_anon_name(struct mm_struct *mm, unsigned long start, > + unsigned long len_in, const char *name) { > + return 0; > +} > +#endif You want to make this depend on CONFIG_PROC_FS. [...] > +#ifdef CONFIG_MMU > + > +#define ANON_VMA_NAME_MAX_LEN 64 > + > +static int prctl_set_vma(unsigned long opt, unsigned long addr, > + unsigned long size, unsigned long arg) > +{ > + struct mm_struct *mm = current->mm; > + char *name, *pch; > + int error; > + > + switch (opt) { > + case PR_SET_VMA_ANON_NAME: > + name = strndup_user((const char __user *)arg, > + ANON_VMA_NAME_MAX_LEN); > + > + if (IS_ERR(name)) > + return PTR_ERR(name); unless I am missing something NULL name would lead to an error rather than a name clearing as advertised above. > + > + for (pch = name; *pch != '\0'; pch++) { > + if (!isprint(*pch)) { > + kfree(name); > + return -EINVAL; > + } > + } > + > + mmap_write_lock(mm); > + error = madvise_set_anon_name(mm, addr, size, name); > + mmap_write_unlock(mm); > + kfree(name); > + break; > + default: > + error = -EINVAL; > + } > + > + return error;
On Fri 27-08-21 12:18:57, Suren Baghdasaryan wrote: [...] > +static void replace_vma_anon_name(struct vm_area_struct *vma, const char *name) > +{ > + if (!name) { > + free_vma_anon_name(vma); > + return; > + } > + > + if (vma->anon_name) { > + /* Should never happen, to dup use dup_vma_anon_name() */ > + WARN_ON(vma->anon_name == name); What is the point of this warning? > + > + /* Same name, nothing to do here */ > + if (!strcmp(name, vma->anon_name)) > + return; > + > + free_vma_anon_name(vma); > + } > + vma->anon_name = kstrdup(name, GFP_KERNEL); > +}
On Wed, Sep 1, 2021 at 1:09 AM 'Michal Hocko' via kernel-team <kernel-team@android.com> wrote: > > On Fri 27-08-21 12:18:57, Suren Baghdasaryan wrote: > [...] > > Userspace can set the name for a region of memory by calling > > prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, start, len, (unsigned long)name); > > Setting the name to NULL clears it. > > Maybe I am missing this part but I do not see this being handled > anywhere. It's handled in replace_vma_anon_name(). When name==NULL we call free_vma_anon_name() which frees and resets anon_name pointer. Except that, as you noticed, the check after strndup_user() will prevent NULL to be passed here. I forgot to test this case after conversion to strndup_user() and missed this important point. Thanks for pointing it out. Will fix and retest. > > [...] > > @@ -3283,5 +3283,16 @@ static inline int seal_check_future_write(int seals, struct vm_area_struct *vma) > > return 0; > > } > > > > +#ifdef CONFIG_ADVISE_SYSCALLS > > +int madvise_set_anon_name(struct mm_struct *mm, unsigned long start, > > + unsigned long len_in, const char *name); > > +#else > > +static inline int > > +madvise_set_anon_name(struct mm_struct *mm, unsigned long start, > > + unsigned long len_in, const char *name) { > > + return 0; > > +} > > +#endif > > You want to make this depend on CONFIG_PROC_FS. Ack. > > [...] > > +#ifdef CONFIG_MMU > > + > > +#define ANON_VMA_NAME_MAX_LEN 64 > > + > > +static int prctl_set_vma(unsigned long opt, unsigned long addr, > > + unsigned long size, unsigned long arg) > > +{ > > + struct mm_struct *mm = current->mm; > > + char *name, *pch; > > + int error; > > + > > + switch (opt) { > > + case PR_SET_VMA_ANON_NAME: > > + name = strndup_user((const char __user *)arg, > > + ANON_VMA_NAME_MAX_LEN); > > + > > + if (IS_ERR(name)) > > + return PTR_ERR(name); > > unless I am missing something NULL name would lead to an error rather > than a name clearing as advertised above. Correct, I missed that. Will fix. > > > + > > + for (pch = name; *pch != '\0'; pch++) { > > + if (!isprint(*pch)) { > > + kfree(name); > > + return -EINVAL; > > + } > > + } > > + > > + mmap_write_lock(mm); > > + error = madvise_set_anon_name(mm, addr, size, name); > > + mmap_write_unlock(mm); > > + kfree(name); > > + break; > > + default: > > + error = -EINVAL; > > + } > > + > > + return error; > -- > Michal Hocko > SUSE Labs > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >
On Wed, Sep 1, 2021 at 1:10 AM 'Michal Hocko' via kernel-team <kernel-team@android.com> wrote: > > On Fri 27-08-21 12:18:57, Suren Baghdasaryan wrote: > [...] > > +static void replace_vma_anon_name(struct vm_area_struct *vma, const char *name) > > +{ > > + if (!name) { > > + free_vma_anon_name(vma); > > + return; > > + } > > + > > + if (vma->anon_name) { > > + /* Should never happen, to dup use dup_vma_anon_name() */ > > + WARN_ON(vma->anon_name == name); > > What is the point of this warning? I wanted to make sure replace_vma_anon_name() is not used from inside vm_area_dup() or some similar place (does not exist today but maybe in the future) where "new" vma is a copy of "orig" vma and new->anon_name==orig->anon_name. If someone by mistake calls replace_vma_anon_name(new, orig->anon_name) and new->anon_name==orig->anon_name then they will keep pointing to the same name pointer, which breaks an assumption that ->anon_name pointers are not shared among vmas even if the string is the same. That would eventually lead to use-after-free error. After the next patch implementing refcounting, the similar situation would lead to both new and orig vma pointing to the same anon_vma_name structure without raising the refcount, which would also lead to use-after-free error. That's why the above comment asks to use dup_vma_anon_name() if this warning ever happens. I can remove the warning but I thought the problem is subtle enough to put some safeguards. > > > + > > + /* Same name, nothing to do here */ > > + if (!strcmp(name, vma->anon_name)) > > + return; > > + > > + free_vma_anon_name(vma); > > + } > > + vma->anon_name = kstrdup(name, GFP_KERNEL); > > +} > -- > Michal Hocko > SUSE Labs > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >
On Wed 01-09-21 08:42:29, Suren Baghdasaryan wrote: > On Wed, Sep 1, 2021 at 1:10 AM 'Michal Hocko' via kernel-team > <kernel-team@android.com> wrote: > > > > On Fri 27-08-21 12:18:57, Suren Baghdasaryan wrote: > > [...] > > > +static void replace_vma_anon_name(struct vm_area_struct *vma, const char *name) > > > +{ > > > + if (!name) { > > > + free_vma_anon_name(vma); > > > + return; > > > + } > > > + > > > + if (vma->anon_name) { > > > + /* Should never happen, to dup use dup_vma_anon_name() */ > > > + WARN_ON(vma->anon_name == name); > > > > What is the point of this warning? > > I wanted to make sure replace_vma_anon_name() is not used from inside > vm_area_dup() or some similar place (does not exist today but maybe in > the future) where "new" vma is a copy of "orig" vma and > new->anon_name==orig->anon_name. If someone by mistake calls > replace_vma_anon_name(new, orig->anon_name) and > new->anon_name==orig->anon_name then they will keep pointing to the > same name pointer, which breaks an assumption that ->anon_name > pointers are not shared among vmas even if the string is the same. > That would eventually lead to use-after-free error. After the next > patch implementing refcounting, the similar situation would lead to > both new and orig vma pointing to the same anon_vma_name structure > without raising the refcount, which would also lead to use-after-free > error. That's why the above comment asks to use dup_vma_anon_name() if > this warning ever happens. > I can remove the warning but I thought the problem is subtle enough to > put some safeguards. This to me sounds very much like a debugging code that shouldn't make it to the final patch to be merged. I do see your point of an early diagnostic but we are talking about an internal MM code and that is not really designed to be robust against its own failures so I do not see why this should be any special.
On Fri, Sep 3, 2021 at 4:49 AM 'Michal Hocko' via kernel-team <kernel-team@android.com> wrote: > > On Wed 01-09-21 08:42:29, Suren Baghdasaryan wrote: > > On Wed, Sep 1, 2021 at 1:10 AM 'Michal Hocko' via kernel-team > > <kernel-team@android.com> wrote: > > > > > > On Fri 27-08-21 12:18:57, Suren Baghdasaryan wrote: > > > [...] > > > > +static void replace_vma_anon_name(struct vm_area_struct *vma, const char *name) > > > > +{ > > > > + if (!name) { > > > > + free_vma_anon_name(vma); > > > > + return; > > > > + } > > > > + > > > > + if (vma->anon_name) { > > > > + /* Should never happen, to dup use dup_vma_anon_name() */ > > > > + WARN_ON(vma->anon_name == name); > > > > > > What is the point of this warning? > > > > I wanted to make sure replace_vma_anon_name() is not used from inside > > vm_area_dup() or some similar place (does not exist today but maybe in > > the future) where "new" vma is a copy of "orig" vma and > > new->anon_name==orig->anon_name. If someone by mistake calls > > replace_vma_anon_name(new, orig->anon_name) and > > new->anon_name==orig->anon_name then they will keep pointing to the > > same name pointer, which breaks an assumption that ->anon_name > > pointers are not shared among vmas even if the string is the same. > > That would eventually lead to use-after-free error. After the next > > patch implementing refcounting, the similar situation would lead to > > both new and orig vma pointing to the same anon_vma_name structure > > without raising the refcount, which would also lead to use-after-free > > error. That's why the above comment asks to use dup_vma_anon_name() if > > this warning ever happens. > > I can remove the warning but I thought the problem is subtle enough to > > put some safeguards. > > This to me sounds very much like a debugging code that shouldn't make it > to the final patch to be merged. I do see your point of an early > diagnostic but we are talking about an internal MM code and that is not > really designed to be robust against its own failures so I do not see > why this should be any special. Fair enough. I posted v9 yesterday but will respin another version in a couple days. Will remove the warning then. Thanks, Suren. > -- > Michal Hocko > SUSE Labs > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 042c418f4090..a067eec54ef1 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -431,6 +431,8 @@ is not associated with a file: [stack] the stack of the main process [vdso] the "virtual dynamic shared object", the kernel system call handler +[anon:<name>] an anonymous mapping that has been + named by userspace ======= ==================================== or if empty, the mapping is anonymous. diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index eb97468dfe4c..2ce5b3c4e7fc 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -308,6 +308,8 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma) name = arch_vma_name(vma); if (!name) { + const char *anon_name; + if (!mm) { name = "[vdso]"; goto done; @@ -319,8 +321,18 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma) goto done; } - if (is_stack(vma)) + if (is_stack(vma)) { name = "[stack]"; + goto done; + } + + anon_name = vma_anon_name(vma); + if (anon_name) { + seq_pad(m, ' '); + seq_puts(m, "[anon:"); + seq_write(m, anon_name, strlen(anon_name)); + seq_putc(m, ']'); + } } done: diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 5c2d806e6ae5..5057843fb71a 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -876,7 +876,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file) new_flags, vma->anon_vma, vma->vm_file, vma->vm_pgoff, vma_policy(vma), - NULL_VM_UFFD_CTX); + NULL_VM_UFFD_CTX, vma_anon_name(vma)); if (prev) vma = prev; else @@ -1440,7 +1440,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, prev = vma_merge(mm, prev, start, vma_end, new_flags, vma->anon_vma, vma->vm_file, vma->vm_pgoff, vma_policy(vma), - ((struct vm_userfaultfd_ctx){ ctx })); + ((struct vm_userfaultfd_ctx){ ctx }), + vma_anon_name(vma)); if (prev) { vma = prev; goto next; @@ -1617,7 +1618,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, prev = vma_merge(mm, prev, start, vma_end, new_flags, vma->anon_vma, vma->vm_file, vma->vm_pgoff, vma_policy(vma), - NULL_VM_UFFD_CTX); + NULL_VM_UFFD_CTX, vma_anon_name(vma)); if (prev) { vma = prev; goto next; diff --git a/include/linux/mm.h b/include/linux/mm.h index 7ca22e6e694a..45c003fae7fe 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2548,7 +2548,7 @@ static inline int vma_adjust(struct vm_area_struct *vma, unsigned long start, extern struct vm_area_struct *vma_merge(struct mm_struct *, struct vm_area_struct *prev, unsigned long addr, unsigned long end, unsigned long vm_flags, struct anon_vma *, struct file *, pgoff_t, - struct mempolicy *, struct vm_userfaultfd_ctx); + struct mempolicy *, struct vm_userfaultfd_ctx, const char *); extern struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *); extern int __split_vma(struct mm_struct *, struct vm_area_struct *, unsigned long addr, int new_below); @@ -3283,5 +3283,16 @@ static inline int seal_check_future_write(int seals, struct vm_area_struct *vma) return 0; } +#ifdef CONFIG_ADVISE_SYSCALLS +int madvise_set_anon_name(struct mm_struct *mm, unsigned long start, + unsigned long len_in, const char *name); +#else +static inline int +madvise_set_anon_name(struct mm_struct *mm, unsigned long start, + unsigned long len_in, const char *name) { + return 0; +} +#endif + #endif /* __KERNEL__ */ #endif /* _LINUX_MM_H */ diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 52bbd2b7cb46..26a30f7a5228 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -342,11 +342,19 @@ struct vm_area_struct { /* * For areas with an address space and backing store, * linkage into the address_space->i_mmap interval tree. + * + * For private anonymous mappings, a pointer to a null terminated string + * containing the name given to the vma, or NULL if unnamed. */ - struct { - struct rb_node rb; - unsigned long rb_subtree_last; - } shared; + + union { + struct { + struct rb_node rb; + unsigned long rb_subtree_last; + } shared; + /* Serialized by mmap_sem. */ + char *anon_name; + }; /* * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma @@ -801,4 +809,36 @@ typedef struct { unsigned long val; } swp_entry_t; +/* + * mmap_lock should be read-locked when calling vma_anon_name() and while using + * the returned pointer. + */ +extern const char *vma_anon_name(struct vm_area_struct *vma); + +/* + * mmap_lock should be read-locked for orig_vma->vm_mm. + * mmap_lock should be write-locked for new_vma->vm_mm or new_vma should be + * isolated. + */ +extern void dup_vma_anon_name(struct vm_area_struct *orig_vma, + struct vm_area_struct *new_vma); + +/* + * mmap_lock should be write-locked or vma should have been isolated under + * write-locked mmap_lock protection. + */ +extern void free_vma_anon_name(struct vm_area_struct *vma); + +/* mmap_lock should be read-locked */ +static inline bool is_same_vma_anon_name(struct vm_area_struct *vma, + const char *name) +{ + const char *vma_name = vma_anon_name(vma); + + if (likely(!vma_name)) + return name == NULL; + + return name && !strcmp(name, vma_name); +} + #endif /* _LINUX_MM_TYPES_H */ diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 967d9c55323d..968582cd91b5 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -267,4 +267,7 @@ struct prctl_mm_map { # define PR_SCHED_CORE_SHARE_FROM 3 /* pull core_sched cookie to pid */ # define PR_SCHED_CORE_MAX 4 +#define PR_SET_VMA 0x53564d41 +# define PR_SET_VMA_ANON_NAME 0 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/fork.c b/kernel/fork.c index 44f4c2d83763..e086f56a4628 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -366,12 +366,14 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig) *new = data_race(*orig); INIT_LIST_HEAD(&new->anon_vma_chain); new->vm_next = new->vm_prev = NULL; + dup_vma_anon_name(orig, new); } return new; } void vm_area_free(struct vm_area_struct *vma) { + free_vma_anon_name(vma); kmem_cache_free(vm_area_cachep, vma); } diff --git a/kernel/sys.c b/kernel/sys.c index ef1a78f5d71c..c48267a8b857 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2298,6 +2298,51 @@ int __weak arch_prctl_spec_ctrl_set(struct task_struct *t, unsigned long which, #define PR_IO_FLUSHER (PF_MEMALLOC_NOIO | PF_LOCAL_THROTTLE) +#ifdef CONFIG_MMU + +#define ANON_VMA_NAME_MAX_LEN 64 + +static int prctl_set_vma(unsigned long opt, unsigned long addr, + unsigned long size, unsigned long arg) +{ + struct mm_struct *mm = current->mm; + char *name, *pch; + int error; + + switch (opt) { + case PR_SET_VMA_ANON_NAME: + name = strndup_user((const char __user *)arg, + ANON_VMA_NAME_MAX_LEN); + + if (IS_ERR(name)) + return PTR_ERR(name); + + for (pch = name; *pch != '\0'; pch++) { + if (!isprint(*pch)) { + kfree(name); + return -EINVAL; + } + } + + mmap_write_lock(mm); + error = madvise_set_anon_name(mm, addr, size, name); + mmap_write_unlock(mm); + kfree(name); + break; + default: + error = -EINVAL; + } + + return error; +} +#else /* CONFIG_MMU */ +static int prctl_set_vma(unsigned long opt, unsigned long start, + unsigned long size, unsigned long arg) +{ + return -EINVAL; +} +#endif + SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, unsigned long, arg4, unsigned long, arg5) { @@ -2567,6 +2612,9 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, error = sched_core_share_pid(arg2, arg3, arg4, arg5); break; #endif + case PR_SET_VMA: + error = prctl_set_vma(arg2, arg3, arg4, arg5); + break; default: error = -EINVAL; break; diff --git a/mm/madvise.c b/mm/madvise.c index 359cd3fa612c..bc029f3fca6a 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -18,6 +18,7 @@ #include <linux/fadvise.h> #include <linux/sched.h> #include <linux/sched/mm.h> +#include <linux/string.h> #include <linux/uio.h> #include <linux/ksm.h> #include <linux/fs.h> @@ -62,19 +63,74 @@ static int madvise_need_mmap_write(int behavior) } } +static inline bool has_vma_anon_name(struct vm_area_struct *vma) +{ + return !vma->vm_file && vma->anon_name; +} + +const char *vma_anon_name(struct vm_area_struct *vma) +{ + if (!has_vma_anon_name(vma)) + return NULL; + + mmap_assert_locked(vma->vm_mm); + + return vma->anon_name; +} + +void dup_vma_anon_name(struct vm_area_struct *orig_vma, + struct vm_area_struct *new_vma) +{ + if (!has_vma_anon_name(orig_vma)) + return; + + new_vma->anon_name = kstrdup(orig_vma->anon_name, GFP_KERNEL); +} + +void free_vma_anon_name(struct vm_area_struct *vma) +{ + if (!has_vma_anon_name(vma)) + return; + + kfree(vma->anon_name); + vma->anon_name = NULL; +} + +/* mmap_lock should be write-locked */ +static void replace_vma_anon_name(struct vm_area_struct *vma, const char *name) +{ + if (!name) { + free_vma_anon_name(vma); + return; + } + + if (vma->anon_name) { + /* Should never happen, to dup use dup_vma_anon_name() */ + WARN_ON(vma->anon_name == name); + + /* Same name, nothing to do here */ + if (!strcmp(name, vma->anon_name)) + return; + + free_vma_anon_name(vma); + } + vma->anon_name = kstrdup(name, GFP_KERNEL); +} + /* - * Update the vm_flags on regiion of a vma, splitting it or merging it as + * Update the vm_flags on region of a vma, splitting it or merging it as * necessary. Must be called with mmap_sem held for writing; */ static int madvise_update_vma(struct vm_area_struct *vma, struct vm_area_struct **prev, unsigned long start, - unsigned long end, unsigned long new_flags) + unsigned long end, unsigned long new_flags, + const char *name) { struct mm_struct *mm = vma->vm_mm; int error; pgoff_t pgoff; - if (new_flags == vma->vm_flags) { + if (new_flags == vma->vm_flags && is_same_vma_anon_name(vma, name)) { *prev = vma; return 0; } @@ -82,7 +138,7 @@ static int madvise_update_vma(struct vm_area_struct *vma, pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma), - vma->vm_userfaultfd_ctx); + vma->vm_userfaultfd_ctx, name); if (*prev) { vma = *prev; goto success; @@ -115,10 +171,30 @@ static int madvise_update_vma(struct vm_area_struct *vma, * vm_flags is protected by the mmap_lock held in write mode. */ vma->vm_flags = new_flags; + if (!vma->vm_file) + replace_vma_anon_name(vma, name); return 0; } +static int madvise_vma_anon_name(struct vm_area_struct *vma, + struct vm_area_struct **prev, + unsigned long start, unsigned long end, + unsigned long name) +{ + int error; + + /* Only anonymous mappings can be named */ + if (vma->vm_file) + return -EINVAL; + + error = madvise_update_vma(vma, prev, start, end, vma->vm_flags, + (const char *)name); + if (error == -ENOMEM) + error = -EAGAIN; + return error; +} + #ifdef CONFIG_SWAP static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start, unsigned long end, struct mm_walk *walk) @@ -948,7 +1024,8 @@ static int madvise_vma_behavior(struct vm_area_struct *vma, break; } - error = madvise_update_vma(vma, prev, start, end, new_flags); + error = madvise_update_vma(vma, prev, start, end, new_flags, + vma_anon_name(vma)); out: if (error == -ENOMEM) @@ -1123,6 +1200,31 @@ int madvise_walk_vmas(struct mm_struct *mm, unsigned long start, return unmapped_error; } +int madvise_set_anon_name(struct mm_struct *mm, unsigned long start, + unsigned long len_in, const char *name) +{ + unsigned long end; + unsigned long len; + + if (start & ~PAGE_MASK) + return -EINVAL; + len = (len_in + ~PAGE_MASK) & PAGE_MASK; + + /* Check to see whether len was rounded up from small -ve to zero */ + if (len_in && !len) + return -EINVAL; + + end = start + len; + if (end < start) + return -EINVAL; + + if (end == start) + return 0; + + return madvise_walk_vmas(mm, start, end, (unsigned long)name, + madvise_vma_anon_name); +} + /* * The madvise(2) system call. * diff --git a/mm/mempolicy.c b/mm/mempolicy.c index e32360e90274..cc21ca7e9d40 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -811,7 +811,8 @@ static int mbind_range(struct mm_struct *mm, unsigned long start, ((vmstart - vma->vm_start) >> PAGE_SHIFT); prev = vma_merge(mm, prev, vmstart, vmend, vma->vm_flags, vma->anon_vma, vma->vm_file, pgoff, - new_pol, vma->vm_userfaultfd_ctx); + new_pol, vma->vm_userfaultfd_ctx, + vma_anon_name(vma)); if (prev) { vma = prev; next = vma->vm_next; diff --git a/mm/mlock.c b/mm/mlock.c index 16d2ee160d43..c878515680af 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -511,7 +511,7 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev, pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma), - vma->vm_userfaultfd_ctx); + vma->vm_userfaultfd_ctx, vma_anon_name(vma)); if (*prev) { vma = *prev; goto success; diff --git a/mm/mmap.c b/mm/mmap.c index ca54d36d203a..baf00fbb1f4c 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1032,7 +1032,8 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, */ static inline int is_mergeable_vma(struct vm_area_struct *vma, struct file *file, unsigned long vm_flags, - struct vm_userfaultfd_ctx vm_userfaultfd_ctx) + struct vm_userfaultfd_ctx vm_userfaultfd_ctx, + const char *anon_name) { /* * VM_SOFTDIRTY should not prevent from VMA merging, if we @@ -1050,6 +1051,8 @@ static inline int is_mergeable_vma(struct vm_area_struct *vma, return 0; if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx)) return 0; + if (!is_same_vma_anon_name(vma, anon_name)) + return 0; return 1; } @@ -1082,9 +1085,10 @@ static int can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags, struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff, - struct vm_userfaultfd_ctx vm_userfaultfd_ctx) + struct vm_userfaultfd_ctx vm_userfaultfd_ctx, + const char *anon_name) { - if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) && + if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx, anon_name) && is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) { if (vma->vm_pgoff == vm_pgoff) return 1; @@ -1103,9 +1107,10 @@ static int can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags, struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff, - struct vm_userfaultfd_ctx vm_userfaultfd_ctx) + struct vm_userfaultfd_ctx vm_userfaultfd_ctx, + const char *anon_name) { - if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) && + if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx, anon_name) && is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) { pgoff_t vm_pglen; vm_pglen = vma_pages(vma); @@ -1116,9 +1121,9 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags, } /* - * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out - * whether that can be merged with its predecessor or its successor. - * Or both (it neatly fills a hole). + * Given a mapping request (addr,end,vm_flags,file,pgoff,anon_name), + * figure out whether that can be merged with its predecessor or its + * successor. Or both (it neatly fills a hole). * * In most cases - when called for mmap, brk or mremap - [addr,end) is * certain not to be mapped by the time vma_merge is called; but when @@ -1163,7 +1168,8 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, unsigned long end, unsigned long vm_flags, struct anon_vma *anon_vma, struct file *file, pgoff_t pgoff, struct mempolicy *policy, - struct vm_userfaultfd_ctx vm_userfaultfd_ctx) + struct vm_userfaultfd_ctx vm_userfaultfd_ctx, + const char *anon_name) { pgoff_t pglen = (end - addr) >> PAGE_SHIFT; struct vm_area_struct *area, *next; @@ -1193,7 +1199,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, mpol_equal(vma_policy(prev), policy) && can_vma_merge_after(prev, vm_flags, anon_vma, file, pgoff, - vm_userfaultfd_ctx)) { + vm_userfaultfd_ctx, anon_name)) { /* * OK, it can. Can we now merge in the successor as well? */ @@ -1202,7 +1208,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, can_vma_merge_before(next, vm_flags, anon_vma, file, pgoff+pglen, - vm_userfaultfd_ctx) && + vm_userfaultfd_ctx, anon_name) && is_mergeable_anon_vma(prev->anon_vma, next->anon_vma, NULL)) { /* cases 1, 6 */ @@ -1225,7 +1231,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, mpol_equal(policy, vma_policy(next)) && can_vma_merge_before(next, vm_flags, anon_vma, file, pgoff+pglen, - vm_userfaultfd_ctx)) { + vm_userfaultfd_ctx, anon_name)) { if (prev && addr < prev->vm_end) /* case 4 */ err = __vma_adjust(prev, prev->vm_start, addr, prev->vm_pgoff, NULL, next); @@ -1766,7 +1772,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, * Can we just expand an old mapping? */ vma = vma_merge(mm, prev, addr, addr + len, vm_flags, - NULL, file, pgoff, NULL, NULL_VM_UFFD_CTX); + NULL, file, pgoff, NULL, NULL_VM_UFFD_CTX, NULL); if (vma) goto out; @@ -1825,7 +1831,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, */ if (unlikely(vm_flags != vma->vm_flags && prev)) { merge = vma_merge(mm, prev, vma->vm_start, vma->vm_end, vma->vm_flags, - NULL, vma->vm_file, vma->vm_pgoff, NULL, NULL_VM_UFFD_CTX); + NULL, vma->vm_file, vma->vm_pgoff, NULL, NULL_VM_UFFD_CTX, NULL); if (merge) { /* ->mmap() can change vma->vm_file and fput the original file. So * fput the vma->vm_file here or we would add an extra fput for file @@ -3087,7 +3093,7 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla /* Can we just expand an old private anonymous mapping? */ vma = vma_merge(mm, prev, addr, addr + len, flags, - NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX); + NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX, NULL); if (vma) goto out; @@ -3280,7 +3286,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, return NULL; /* should never get here */ new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags, vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma), - vma->vm_userfaultfd_ctx); + vma->vm_userfaultfd_ctx, vma_anon_name(vma)); if (new_vma) { /* * Source vma may have been merged into new_vma diff --git a/mm/mprotect.c b/mm/mprotect.c index 883e2cc85cad..a48ff8e79f48 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -464,7 +464,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); *pprev = vma_merge(mm, *pprev, start, end, newflags, vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma), - vma->vm_userfaultfd_ctx); + vma->vm_userfaultfd_ctx, vma_anon_name(vma)); if (*pprev) { vma = *pprev; VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY);