| Message ID | 39c4a91f2867684dc51c5395d26cb56ffe9d995d.1652876188.git.esyr@redhat.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | Fix kprobe_multi interface issues for 5.18 | expand |
On 5/18/22 5:22 AM, Eugene Syromiatnikov wrote: > Check that size would not overflow before calculation (and return > -EOVERFLOW if it will), to prevent potential out-of-bounds write > with the following copy_from_user. Add the same check > to kprobe_multi_resolve_syms in case it will be called from elsewhere > in the future. > > Fixes: 0dcac272540613d4 ("bpf: Add multi kprobe link") > Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com> > --- > kernel/trace/bpf_trace.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > index d8553f4..212faa4 100644 > --- a/kernel/trace/bpf_trace.c > +++ b/kernel/trace/bpf_trace.c > @@ -2352,13 +2352,15 @@ static int > kprobe_multi_resolve_syms(const void __user *usyms, u32 cnt, > unsigned long *addrs) > { > - unsigned long addr, size; > + unsigned long addr, sym_size; > + u32 size; > const char __user **syms; > int err = -ENOMEM; > unsigned int i; > char *func; > > - size = cnt * sizeof(*syms); > + if (check_mul_overflow(cnt, (u32)sizeof(*syms), &size)) > + return -EOVERFLOW; In mm/util.c kvmalloc_node(), we have /* Don't even allow crazy sizes */ if (unlikely(size > INT_MAX)) { WARN_ON_ONCE(!(flags & __GFP_NOWARN)); return NULL; } Basically the maximum size to be allocated in INT_MAX. Here, we have 'size' as u32, which means if the size is 0xffff0000, the check_mul_overflow will return false (no overflow) but kvzalloc will still have a warning. I think we should change the type of 'size' to be 'int' which should catch the above case and be consistent with what kvmalloc_node() intends to warn. > syms = kvzalloc(size, GFP_KERNEL); > if (!syms) > return -ENOMEM; > @@ -2382,9 +2384,9 @@ kprobe_multi_resolve_syms(const void __user *usyms, u32 cnt, > addr = kallsyms_lookup_name(func); > if (!addr) > goto error; > - if (!kallsyms_lookup_size_offset(addr, &size, NULL)) > + if (!kallsyms_lookup_size_offset(addr, &sym_size, NULL)) > goto error; > - addr = ftrace_location_range(addr, addr + size - 1); > + addr = ftrace_location_range(addr, addr + sym_size - 1); > if (!addr) > goto error; > addrs[i] = addr; > @@ -2429,7 +2431,8 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr > if (!cnt) > return -EINVAL; > > - size = cnt * sizeof(*addrs); > + if (check_mul_overflow(cnt, (u32)sizeof(*addrs), &size)) > + return -EOVERFLOW; > addrs = kvmalloc(size, GFP_KERNEL); > if (!addrs) > return -ENOMEM;
On Wed, May 18, 2022 at 09:34:22AM -0700, Yonghong Song wrote: > On 5/18/22 5:22 AM, Eugene Syromiatnikov wrote: > >- size = cnt * sizeof(*syms); > >+ if (check_mul_overflow(cnt, (u32)sizeof(*syms), &size)) > >+ return -EOVERFLOW; > > In mm/util.c kvmalloc_node(), we have > > /* Don't even allow crazy sizes */ > if (unlikely(size > INT_MAX)) { > WARN_ON_ONCE(!(flags & __GFP_NOWARN)); > return NULL; > } > > Basically the maximum size to be allocated in INT_MAX. > > Here, we have 'size' as u32, which means if the size is 0xffff0000, > the check_mul_overflow will return false (no overflow) but > kvzalloc will still have a warning. > > I think we should change the type of 'size' to be 'int' which > should catch the above case and be consistent with > what kvmalloc_node() intends to warn. Huh, it's a bitmore complicated as check_mul_overflow requires types to match; what do you think about + if (check_mul_overflow(cnt, (u32)sizeof(*syms), &size) || size > INT_MAX) ?
On 5/18/22 1:00 PM, Eugene Syromiatnikov wrote: > On Wed, May 18, 2022 at 09:34:22AM -0700, Yonghong Song wrote: >> On 5/18/22 5:22 AM, Eugene Syromiatnikov wrote: >>> - size = cnt * sizeof(*syms); >>> + if (check_mul_overflow(cnt, (u32)sizeof(*syms), &size)) >>> + return -EOVERFLOW; >> >> In mm/util.c kvmalloc_node(), we have >> >> /* Don't even allow crazy sizes */ >> if (unlikely(size > INT_MAX)) { >> WARN_ON_ONCE(!(flags & __GFP_NOWARN)); >> return NULL; >> } >> >> Basically the maximum size to be allocated in INT_MAX. >> >> Here, we have 'size' as u32, which means if the size is 0xffff0000, >> the check_mul_overflow will return false (no overflow) but >> kvzalloc will still have a warning. >> >> I think we should change the type of 'size' to be 'int' which >> should catch the above case and be consistent with >> what kvmalloc_node() intends to warn. > > Huh, it's a bitmore complicated as check_mul_overflow requires types to > match; what do you think about > > + if (check_mul_overflow(cnt, (u32)sizeof(*syms), &size) || size > INT_MAX) > > ? This works for me.
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index d8553f4..212faa4 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2352,13 +2352,15 @@ static int kprobe_multi_resolve_syms(const void __user *usyms, u32 cnt, unsigned long *addrs) { - unsigned long addr, size; + unsigned long addr, sym_size; + u32 size; const char __user **syms; int err = -ENOMEM; unsigned int i; char *func; - size = cnt * sizeof(*syms); + if (check_mul_overflow(cnt, (u32)sizeof(*syms), &size)) + return -EOVERFLOW; syms = kvzalloc(size, GFP_KERNEL); if (!syms) return -ENOMEM; @@ -2382,9 +2384,9 @@ kprobe_multi_resolve_syms(const void __user *usyms, u32 cnt, addr = kallsyms_lookup_name(func); if (!addr) goto error; - if (!kallsyms_lookup_size_offset(addr, &size, NULL)) + if (!kallsyms_lookup_size_offset(addr, &sym_size, NULL)) goto error; - addr = ftrace_location_range(addr, addr + size - 1); + addr = ftrace_location_range(addr, addr + sym_size - 1); if (!addr) goto error; addrs[i] = addr; @@ -2429,7 +2431,8 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr if (!cnt) return -EINVAL; - size = cnt * sizeof(*addrs); + if (check_mul_overflow(cnt, (u32)sizeof(*addrs), &size)) + return -EOVERFLOW; addrs = kvmalloc(size, GFP_KERNEL); if (!addrs) return -ENOMEM;
Check that size would not overflow before calculation (and return -EOVERFLOW if it will), to prevent potential out-of-bounds write with the following copy_from_user. Add the same check to kprobe_multi_resolve_syms in case it will be called from elsewhere in the future. Fixes: 0dcac272540613d4 ("bpf: Add multi kprobe link") Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com> --- kernel/trace/bpf_trace.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)