On Wed, Mar 04, 2020 at 09:34:49AM -0800, Randy Dunlap wrote: > On 3/3/20 10:28 PM, akpm@xxxxxxxxxxxxxxxxxxxx wrote: > > The mm-of-the-moment snapshot 2020-03-03-22-28 has been uploaded to > > > > http://www.ozlabs.org/~akpm/mmotm/ > > > > mmotm-readme.txt says > > > > README for mm-of-the-moment: > > > > http://www.ozlabs.org/~akpm/mmotm/ > > > > This is a snapshot of my -mm patch queue. Uploaded at random hopefully > > more than once a week. > > > > You will need quilt to apply these patches to the latest Linus release (5.x > > or 5.x-rcY). The series file is in broken-out.tar.gz and is duplicated in > > http://ozlabs.org/~akpm/mmotm/series > > on x86_64: > > mm/kasan/common.o: warning: objtool: kasan_report()+0x13: call to report_enabled() with UACCESS enabled I used next/master instead, and found the below broken commit responsible for this. --- commit 97f4ea76d4f40a401b84825f038710c9a96ec294 Author: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Date: Wed Mar 4 22:31:15 2020 +1100 kasan: detect negative size in memory operation function Patch series "fix the missing underflow in memory operation function", v4. The patchset helps to produce a KASAN report when size is negative in memory operation functions. It is helpful for programmer to solve an undefined behavior issue. Patch 1 based on Dmitry's review and suggestion, patch 2 is a test in order to verify the patch 1. [1]https://bugzilla.kernel.org/show_bug.cgi?id=199341 [2]https://lore.kernel.org/linux-arm-kernel/20190927034338.15813-1-walter-zh.wu@xxxxxxxxxxxx/ This patch (of 2): KASAN missed detecting size is a negative number in memset(), memcpy(), and memmove(), it will cause out-of-bounds bug. So needs to be detected by KASAN. If size is a negative number, then it has a reason to be defined as out-of-bounds bug type. Casting negative numbers to size_t would indeed turn up as a large size_t and its value will be larger than ULONG_MAX/2, so that this can qualify as out-of-bounds. KASAN report is shown below: BUG: KASAN: out-of-bounds in kmalloc_memmove_invalid_size+0x70/0xa0 Read of size 18446744073709551608 at addr ffffff8069660904 by task cat/72 CPU: 2 PID: 72 Comm: cat Not tainted 5.4.0-rc1-next-20191004ajb-00001-gdb8af2f372b2-dirty #1 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x0/0x288 show_stack+0x14/0x20 dump_stack+0x10c/0x164 print_address_description.isra.9+0x68/0x378 __kasan_report+0x164/0x1a0 kasan_report+0xc/0x18 check_memory_region+0x174/0x1d0 memmove+0x34/0x88 kmalloc_memmove_invalid_size+0x70/0xa0 [1] https://bugzilla.kernel.org/show_bug.cgi?id=199341 Link: http://lkml.kernel.org/r/20191112065302.7015-1-walter-zh.wu@xxxxxxxxxxxx Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Reported-by: kernel test robot <lkp@xxxxxxxxx> Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 5cde9e7c2664..31314ca7c635 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -190,7 +190,7 @@ void kasan_init_tags(void); void *kasan_reset_tag(const void *addr); -void kasan_report(unsigned long addr, size_t size, +bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip); #else /* CONFIG_KASAN_SW_TAGS */ diff --git a/mm/kasan/common.c b/mm/kasan/common.c index 6aa51723b92b..c798b12323d7 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -105,7 +105,8 @@ EXPORT_SYMBOL(__kasan_check_write); #undef memset void *memset(void *addr, int c, size_t len) { - check_memory_region((unsigned long)addr, len, true, _RET_IP_); + if (!check_memory_region((unsigned long)addr, len, true, _RET_IP_)) + return NULL; return __memset(addr, c, len); } @@ -114,8 +115,9 @@ void *memset(void *addr, int c, size_t len) #undef memmove void *memmove(void *dest, const void *src, size_t len) { - check_memory_region((unsigned long)src, len, false, _RET_IP_); - check_memory_region((unsigned long)dest, len, true, _RET_IP_); + if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) || + !check_memory_region((unsigned long)dest, len, true, _RET_IP_)) + return NULL; return __memmove(dest, src, len); } @@ -124,8 +126,9 @@ void *memmove(void *dest, const void *src, size_t len) #undef memcpy void *memcpy(void *dest, const void *src, size_t len) { - check_memory_region((unsigned long)src, len, false, _RET_IP_); - check_memory_region((unsigned long)dest, len, true, _RET_IP_); + if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) || + !check_memory_region((unsigned long)dest, len, true, _RET_IP_)) + return NULL; return __memcpy(dest, src, len); } @@ -634,12 +637,20 @@ void kasan_free_shadow(const struct vm_struct *vm) #endif extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip); +extern bool report_enabled(void); -void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) +bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) { - unsigned long flags = user_access_save(); + unsigned long flags; + + if (likely(!report_enabled())) + return false; + + flags = user_access_save(); __kasan_report(addr, size, is_write, ip); user_access_restore(flags); + + return true; } #ifdef CONFIG_MEMORY_HOTPLUG diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c index 616f9dd82d12..56ff8885fe2e 100644 --- a/mm/kasan/generic.c +++ b/mm/kasan/generic.c @@ -173,17 +173,18 @@ static __always_inline bool check_memory_region_inline(unsigned long addr, if (unlikely(size == 0)) return true; + if (unlikely(addr + size < addr)) + return !kasan_report(addr, size, write, ret_ip); + if (unlikely((void *)addr < kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) { - kasan_report(addr, size, write, ret_ip); - return false; + return !kasan_report(addr, size, write, ret_ip); } if (likely(!memory_is_poisoned(addr, size))) return true; - kasan_report(addr, size, write, ret_ip); - return false; + return !kasan_report(addr, size, write, ret_ip); } bool check_memory_region(unsigned long addr, size_t size, bool write, diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c index 2d97efd4954f..e200acb2d292 100644 --- a/mm/kasan/generic_report.c +++ b/mm/kasan/generic_report.c @@ -110,6 +110,17 @@ static const char *get_wild_bug_type(struct kasan_access_info *info) const char *get_bug_type(struct kasan_access_info *info) { + /* + * If access_size is a negative number, then it has reason to be + * defined as out-of-bounds bug type. + * + * Casting negative numbers to size_t would indeed turn up as + * a large size_t and its value will be larger than ULONG_MAX/2, + * so that this can qualify as out-of-bounds. + */ + if (info->access_addr + info->access_size < info->access_addr) + return "out-of-bounds"; + if (addr_has_shadow(info->access_addr)) return get_shadow_bug_type(info); return get_wild_bug_type(info); diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 3a083274628e..e8f37199d885 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -153,7 +153,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write, void *find_first_bad_addr(void *addr, size_t size); const char *get_bug_type(struct kasan_access_info *info); -void kasan_report(unsigned long addr, size_t size, +bool 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/report.c b/mm/kasan/report.c index 5ef9f24f566b..cf5c17d5e361 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -446,7 +446,7 @@ static void print_shadow_for_address(const void *addr) } } -static bool report_enabled(void) +bool report_enabled(void) { if (current->kasan_depth) return false; @@ -478,9 +478,6 @@ void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned lon void *untagged_addr; unsigned long flags; - if (likely(!report_enabled())) - return; - disable_trace_on_warning(); tagged_addr = (void *)addr; diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c index 0e987c9ca052..25b7734e7013 100644 --- a/mm/kasan/tags.c +++ b/mm/kasan/tags.c @@ -86,6 +86,9 @@ bool check_memory_region(unsigned long addr, size_t size, bool write, if (unlikely(size == 0)) return true; + if (unlikely(addr + size < addr)) + return !kasan_report(addr, size, write, ret_ip); + tag = get_tag((const void *)addr); /* @@ -111,15 +114,13 @@ bool check_memory_region(unsigned long addr, size_t size, bool write, untagged_addr = reset_tag((const void *)addr); if (unlikely(untagged_addr < kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) { - kasan_report(addr, size, write, ret_ip); - return false; + return !kasan_report(addr, size, write, ret_ip); } shadow_first = kasan_mem_to_shadow(untagged_addr); shadow_last = kasan_mem_to_shadow(untagged_addr + size - 1); for (shadow = shadow_first; shadow <= shadow_last; shadow++) { if (*shadow != tag) { - kasan_report(addr, size, write, ret_ip); - return false; + return !kasan_report(addr, size, write, ret_ip); } } diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c index 969ae08f59d7..1d412760551a 100644 --- a/mm/kasan/tags_report.c +++ b/mm/kasan/tags_report.c @@ -36,6 +36,17 @@ const char *get_bug_type(struct kasan_access_info *info) { + /* + * If access_size is a negative number, then it has reason to be + * defined as out-of-bounds bug type. + * + * Casting negative numbers to size_t would indeed turn up as + * a large size_t and its value will be larger than ULONG_MAX/2, + * so that this can qualify as out-of-bounds. + */ + if (info->access_addr + info->access_size < info->access_addr) + return "out-of-bounds"; + #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY struct kasan_alloc_meta *alloc_meta; struct kmem_cache *cache;
