From: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Subject: 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 [cai@xxxxxx: fix -Wdeclaration-after-statement warn] Link: http://lkml.kernel.org/r/1583509030-27939-1-git-send-email-cai@xxxxxx [peterz@xxxxxxxxxxxxx: fix objtool warning] Link: http://lkml.kernel.org/r/20200305095436.GV2596@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/20191112065302.7015-1-walter-zh.wu@xxxxxxxxxxxx Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Signed-off-by: Qian Cai <cai@xxxxxx> 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> --- include/linux/kasan.h | 2 +- mm/kasan/common.c | 26 +++++++++++++++++++------- mm/kasan/generic.c | 9 +++++---- mm/kasan/generic_report.c | 11 +++++++++++ mm/kasan/kasan.h | 2 +- mm/kasan/report.c | 5 +---- mm/kasan/tags.c | 9 +++++---- mm/kasan/tags_report.c | 11 +++++++++++ 8 files changed, 54 insertions(+), 21 deletions(-) --- a/include/linux/kasan.h~kasan-detect-negative-size-in-memory-operation-function +++ a/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 */ --- a/mm/kasan/common.c~kasan-detect-negative-size-in-memory-operation-function +++ a/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 l #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 *sr #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 +637,21 @@ void kasan_free_shadow(const struct vm_s #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(); - __kasan_report(addr, size, is_write, ip); + bool ret = false; + + if (likely(report_enabled())) { + __kasan_report(addr, size, is_write, ip); + ret = true; + } + user_access_restore(flags); + + return ret; } #ifdef CONFIG_MEMORY_HOTPLUG --- a/mm/kasan/generic.c~kasan-detect-negative-size-in-memory-operation-function +++ a/mm/kasan/generic.c @@ -173,17 +173,18 @@ static __always_inline bool check_memory 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, --- a/mm/kasan/generic_report.c~kasan-detect-negative-size-in-memory-operation-function +++ a/mm/kasan/generic_report.c @@ -110,6 +110,17 @@ static const char *get_wild_bug_type(str 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); --- a/mm/kasan/kasan.h~kasan-detect-negative-size-in-memory-operation-function +++ a/mm/kasan/kasan.h @@ -153,7 +153,7 @@ bool check_memory_region(unsigned long a 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); --- a/mm/kasan/report.c~kasan-detect-negative-size-in-memory-operation-function +++ a/mm/kasan/report.c @@ -446,7 +446,7 @@ static void print_shadow_for_address(con } } -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, void *untagged_addr; unsigned long flags; - if (likely(!report_enabled())) - return; - disable_trace_on_warning(); tagged_addr = (void *)addr; --- a/mm/kasan/tags.c~kasan-detect-negative-size-in-memory-operation-function +++ a/mm/kasan/tags.c @@ -86,6 +86,9 @@ bool check_memory_region(unsigned long a 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 a 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); } } --- a/mm/kasan/tags_report.c~kasan-detect-negative-size-in-memory-operation-function +++ a/mm/kasan/tags_report.c @@ -60,6 +60,17 @@ const char *get_bug_type(struct kasan_ac } #endif + /* + * 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"; + return "invalid-access"; } _
