| Message ID | f39cdef4fde40b6d2ef356db3e0126bda0e1e8c7.1535462971.git.andreyknvl@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | khwasan: kernel hardware assisted address sanitizer | expand |
On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov <andreyknvl@google.com> wrote: > This commit adds rountines, that print KHWASAN error reports. Those are > quite similar to KASAN, the difference is: > > 1. The way KHWASAN finds the first bad shadow cell (with a mismatching > tag). KHWASAN compares memory tags from the shadow memory to the pointer > tag. > > 2. KHWASAN reports all bugs with the "KASAN: invalid-access" header. This > is done, so various external tools that already parse the kernel logs > looking for KASAN reports wouldn't need to be changed. > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > --- > include/linux/kasan.h | 3 +++ > mm/kasan/kasan.h | 7 +++++ > mm/kasan/kasan_report.c | 7 ++--- > mm/kasan/khwasan_report.c | 21 +++++++++++++++ > mm/kasan/report.c | 57 +++++++++++++++++++++------------------ > 5 files changed, 64 insertions(+), 31 deletions(-) > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > index 1f852244e739..4424359a9dfa 100644 > --- a/include/linux/kasan.h > +++ b/include/linux/kasan.h > @@ -174,6 +174,9 @@ void *khwasan_preset_slub_tag(struct kmem_cache *cache, const void *addr); > void *khwasan_preset_slab_tag(struct kmem_cache *cache, unsigned int idx, > const void *addr); > > +void kasan_report(unsigned long addr, size_t size, > + bool write, unsigned long ip); > + > #else /* CONFIG_KASAN_HW */ > > static inline void khwasan_init(void) { } > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 82672473740c..d60859d26be7 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -119,8 +119,15 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value); > void check_memory_region(unsigned long addr, size_t size, bool write, > unsigned long ret_ip); > > +void *find_first_bad_addr(void *addr, size_t size); > const char *get_bug_type(struct kasan_access_info *info); > > +#ifdef CONFIG_KASAN_HW We already have #ifdef CONFIG_KASAN_HW section below with additional functions for KASAN_HW and empty stubs otherwise. I would add this one there as well. > +void print_tags(u8 addr_tag, const void *addr); > +#else > +static inline void print_tags(u8 addr_tag, const void *addr) { } > +#endif > + > void kasan_report(unsigned long addr, size_t size, > bool is_write, unsigned long ip); > void kasan_report_invalid_free(void *object, unsigned long ip); > diff --git a/mm/kasan/kasan_report.c b/mm/kasan/kasan_report.c > index 2d8decbecbd5..fdf2d77e3125 100644 > --- a/mm/kasan/kasan_report.c > +++ b/mm/kasan/kasan_report.c > @@ -33,10 +33,10 @@ > #include "kasan.h" > #include "../slab.h" > > -static const void *find_first_bad_addr(const void *addr, size_t size) > +void *find_first_bad_addr(void *addr, size_t size) > { > u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr); > - const void *first_bad_addr = addr; > + void *first_bad_addr = addr; > > while (!shadow_val && first_bad_addr < addr + size) { > first_bad_addr += KASAN_SHADOW_SCALE_SIZE; > @@ -50,9 +50,6 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info) > const char *bug_type = "unknown-crash"; > u8 *shadow_addr; > > - info->first_bad_addr = find_first_bad_addr(info->access_addr, > - info->access_size); > - > shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr); > > /* > diff --git a/mm/kasan/khwasan_report.c b/mm/kasan/khwasan_report.c > index 2edbc3c76be5..51238b404b08 100644 > --- a/mm/kasan/khwasan_report.c > +++ b/mm/kasan/khwasan_report.c > @@ -37,3 +37,24 @@ const char *get_bug_type(struct kasan_access_info *info) > { > return "invalid-access"; > } > + > +void *find_first_bad_addr(void *addr, size_t size) > +{ > + u8 tag = get_tag(addr); > + void *untagged_addr = reset_tag(addr); > + u8 *shadow = (u8 *)kasan_mem_to_shadow(untagged_addr); > + void *first_bad_addr = untagged_addr; > + > + while (*shadow == tag && first_bad_addr < untagged_addr + size) { I think it's better to check that are within bounds before accessing shadow. Otherwise it's kinda potential out-of-bounds access ;) I know that we _should_ not do an oob here, but still. Also feels that this function can be shortened to something like: u8 tag = get_tag(addr); void *p = reset_tag(addr); void *end = p + size; while (p < end && tag == *(u8 *)kasan_mem_to_shadow(p)) p += KASAN_SHADOW_SCALE_SIZE; return p; > + first_bad_addr += KASAN_SHADOW_SCALE_SIZE; > + shadow = (u8 *)kasan_mem_to_shadow(first_bad_addr); > + } > + return first_bad_addr; > +} > + > +void print_tags(u8 addr_tag, const void *addr) > +{ > + u8 *shadow = (u8 *)kasan_mem_to_shadow(addr); > + > + pr_err("Pointer tag: [%02x], memory tag: [%02x]\n", addr_tag, *shadow); > +} > diff --git a/mm/kasan/report.c b/mm/kasan/report.c > index 155247a6f8a8..e031c78f2e52 100644 > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -64,11 +64,10 @@ static int __init kasan_set_multi_shot(char *str) > } > __setup("kasan_multi_shot", kasan_set_multi_shot); > > -static void print_error_description(struct kasan_access_info *info, > - const char *bug_type) > +static void print_error_description(struct kasan_access_info *info) > { > pr_err("BUG: KASAN: %s in %pS\n", > - bug_type, (void *)info->ip); > + get_bug_type(info), (void *)info->ip); > pr_err("%s of size %zu at addr %px by task %s/%d\n", > info->is_write ? "Write" : "Read", info->access_size, > info->access_addr, current->comm, task_pid_nr(current)); > @@ -272,6 +271,8 @@ void kasan_report_invalid_free(void *object, unsigned long ip) > > start_report(&flags); > pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip); > + print_tags(get_tag(object), reset_tag(object)); > + object = reset_tag(object); > pr_err("\n"); > print_address_description(object); > pr_err("\n"); > @@ -279,41 +280,45 @@ void kasan_report_invalid_free(void *object, unsigned long ip) > end_report(&flags); > } > > -static void kasan_report_error(struct kasan_access_info *info) > -{ > - unsigned long flags; > - > - start_report(&flags); > - > - print_error_description(info, get_bug_type(info)); > - pr_err("\n"); > - > - if (!addr_has_shadow(info->access_addr)) { > - dump_stack(); > - } else { > - print_address_description((void *)info->access_addr); > - pr_err("\n"); > - print_shadow_for_address(info->first_bad_addr); > - } > - > - end_report(&flags); > -} > - > void kasan_report(unsigned long addr, size_t size, > bool is_write, unsigned long ip) > { > struct kasan_access_info info; > + void *tagged_addr; > + void *untagged_addr; > + unsigned long flags; > > if (likely(!report_enabled())) > return; > > disable_trace_on_warning(); > > - info.access_addr = (void *)addr; > - info.first_bad_addr = (void *)addr; > + tagged_addr = (void *)addr; > + untagged_addr = reset_tag(tagged_addr); > + > + info.access_addr = tagged_addr; > + if (addr_has_shadow(untagged_addr)) > + info.first_bad_addr = find_first_bad_addr(tagged_addr, size); > + else > + info.first_bad_addr = untagged_addr; > info.access_size = size; > info.is_write = is_write; > info.ip = ip; > > - kasan_report_error(&info); > + start_report(&flags); > + > + print_error_description(&info); > + if (addr_has_shadow(untagged_addr)) > + print_tags(get_tag(tagged_addr), info.first_bad_addr); > + pr_err("\n"); > + > + if (addr_has_shadow(untagged_addr)) { > + print_address_description(untagged_addr); > + pr_err("\n"); > + print_shadow_for_address(info.first_bad_addr); > + } else { > + dump_stack(); > + } > + > + end_report(&flags); > } > -- > 2.19.0.rc0.228.g281dcd1b4d0-goog >
On Wed, Sep 12, 2018 at 7:50 PM, Dmitry Vyukov <dvyukov@google.com> wrote: > On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov <andreyknvl@google.com> wrote: >> +#ifdef CONFIG_KASAN_HW > > We already have #ifdef CONFIG_KASAN_HW section below with additional > functions for KASAN_HW and empty stubs otherwise. I would add this one > there as well. Will do in v7. > >> +void print_tags(u8 addr_tag, const void *addr); >> +#else >> +static inline void print_tags(u8 addr_tag, const void *addr) { } >> +#endif >> +void *find_first_bad_addr(void *addr, size_t size) >> +{ >> + u8 tag = get_tag(addr); >> + void *untagged_addr = reset_tag(addr); >> + u8 *shadow = (u8 *)kasan_mem_to_shadow(untagged_addr); >> + void *first_bad_addr = untagged_addr; >> + >> + while (*shadow == tag && first_bad_addr < untagged_addr + size) { > > I think it's better to check that are within bounds before accessing > shadow. Otherwise it's kinda potential out-of-bounds access ;) > I know that we _should_ not do an oob here, but still. > Also feels that this function can be shortened to something like: > > u8 tag = get_tag(addr); > void *p = reset_tag(addr); > void *end = p + size; > > while (p < end && tag == *(u8 *)kasan_mem_to_shadow(p)) > p += KASAN_SHADOW_SCALE_SIZE; > return p; Will do in v7.
diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 1f852244e739..4424359a9dfa 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -174,6 +174,9 @@ void *khwasan_preset_slub_tag(struct kmem_cache *cache, const void *addr); void *khwasan_preset_slab_tag(struct kmem_cache *cache, unsigned int idx, const void *addr); +void kasan_report(unsigned long addr, size_t size, + bool write, unsigned long ip); + #else /* CONFIG_KASAN_HW */ static inline void khwasan_init(void) { } diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 82672473740c..d60859d26be7 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -119,8 +119,15 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value); void check_memory_region(unsigned long addr, size_t size, bool write, unsigned long ret_ip); +void *find_first_bad_addr(void *addr, size_t size); const char *get_bug_type(struct kasan_access_info *info); +#ifdef CONFIG_KASAN_HW +void print_tags(u8 addr_tag, const void *addr); +#else +static inline void print_tags(u8 addr_tag, const void *addr) { } +#endif + void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip); void kasan_report_invalid_free(void *object, unsigned long ip); diff --git a/mm/kasan/kasan_report.c b/mm/kasan/kasan_report.c index 2d8decbecbd5..fdf2d77e3125 100644 --- a/mm/kasan/kasan_report.c +++ b/mm/kasan/kasan_report.c @@ -33,10 +33,10 @@ #include "kasan.h" #include "../slab.h" -static const void *find_first_bad_addr(const void *addr, size_t size) +void *find_first_bad_addr(void *addr, size_t size) { u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr); - const void *first_bad_addr = addr; + void *first_bad_addr = addr; while (!shadow_val && first_bad_addr < addr + size) { first_bad_addr += KASAN_SHADOW_SCALE_SIZE; @@ -50,9 +50,6 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info) const char *bug_type = "unknown-crash"; u8 *shadow_addr; - info->first_bad_addr = find_first_bad_addr(info->access_addr, - info->access_size); - shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr); /* diff --git a/mm/kasan/khwasan_report.c b/mm/kasan/khwasan_report.c index 2edbc3c76be5..51238b404b08 100644 --- a/mm/kasan/khwasan_report.c +++ b/mm/kasan/khwasan_report.c @@ -37,3 +37,24 @@ const char *get_bug_type(struct kasan_access_info *info) { return "invalid-access"; } + +void *find_first_bad_addr(void *addr, size_t size) +{ + u8 tag = get_tag(addr); + void *untagged_addr = reset_tag(addr); + u8 *shadow = (u8 *)kasan_mem_to_shadow(untagged_addr); + void *first_bad_addr = untagged_addr; + + while (*shadow == tag && first_bad_addr < untagged_addr + size) { + first_bad_addr += KASAN_SHADOW_SCALE_SIZE; + shadow = (u8 *)kasan_mem_to_shadow(first_bad_addr); + } + return first_bad_addr; +} + +void print_tags(u8 addr_tag, const void *addr) +{ + u8 *shadow = (u8 *)kasan_mem_to_shadow(addr); + + pr_err("Pointer tag: [%02x], memory tag: [%02x]\n", addr_tag, *shadow); +} diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 155247a6f8a8..e031c78f2e52 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -64,11 +64,10 @@ static int __init kasan_set_multi_shot(char *str) } __setup("kasan_multi_shot", kasan_set_multi_shot); -static void print_error_description(struct kasan_access_info *info, - const char *bug_type) +static void print_error_description(struct kasan_access_info *info) { pr_err("BUG: KASAN: %s in %pS\n", - bug_type, (void *)info->ip); + get_bug_type(info), (void *)info->ip); pr_err("%s of size %zu at addr %px by task %s/%d\n", info->is_write ? "Write" : "Read", info->access_size, info->access_addr, current->comm, task_pid_nr(current)); @@ -272,6 +271,8 @@ void kasan_report_invalid_free(void *object, unsigned long ip) start_report(&flags); pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip); + print_tags(get_tag(object), reset_tag(object)); + object = reset_tag(object); pr_err("\n"); print_address_description(object); pr_err("\n"); @@ -279,41 +280,45 @@ void kasan_report_invalid_free(void *object, unsigned long ip) end_report(&flags); } -static void kasan_report_error(struct kasan_access_info *info) -{ - unsigned long flags; - - start_report(&flags); - - print_error_description(info, get_bug_type(info)); - pr_err("\n"); - - if (!addr_has_shadow(info->access_addr)) { - dump_stack(); - } else { - print_address_description((void *)info->access_addr); - pr_err("\n"); - print_shadow_for_address(info->first_bad_addr); - } - - end_report(&flags); -} - void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) { struct kasan_access_info info; + void *tagged_addr; + void *untagged_addr; + unsigned long flags; if (likely(!report_enabled())) return; disable_trace_on_warning(); - info.access_addr = (void *)addr; - info.first_bad_addr = (void *)addr; + tagged_addr = (void *)addr; + untagged_addr = reset_tag(tagged_addr); + + info.access_addr = tagged_addr; + if (addr_has_shadow(untagged_addr)) + info.first_bad_addr = find_first_bad_addr(tagged_addr, size); + else + info.first_bad_addr = untagged_addr; info.access_size = size; info.is_write = is_write; info.ip = ip; - kasan_report_error(&info); + start_report(&flags); + + print_error_description(&info); + if (addr_has_shadow(untagged_addr)) + print_tags(get_tag(tagged_addr), info.first_bad_addr); + pr_err("\n"); + + if (addr_has_shadow(untagged_addr)) { + print_address_description(untagged_addr); + pr_err("\n"); + print_shadow_for_address(info.first_bad_addr); + } else { + dump_stack(); + } + + end_report(&flags); }
This commit adds rountines, that print KHWASAN error reports. Those are quite similar to KASAN, the difference is: 1. The way KHWASAN finds the first bad shadow cell (with a mismatching tag). KHWASAN compares memory tags from the shadow memory to the pointer tag. 2. KHWASAN reports all bugs with the "KASAN: invalid-access" header. This is done, so various external tools that already parse the kernel logs looking for KASAN reports wouldn't need to be changed. Signed-off-by: Andrey Konovalov <andreyknvl@google.com> --- include/linux/kasan.h | 3 +++ mm/kasan/kasan.h | 7 +++++ mm/kasan/kasan_report.c | 7 ++--- mm/kasan/khwasan_report.c | 21 +++++++++++++++ mm/kasan/report.c | 57 +++++++++++++++++++++------------------ 5 files changed, 64 insertions(+), 31 deletions(-)