On Mon, 2019-10-07 at 15:33 +0200, Dmitry Vyukov wrote: > On Mon, Oct 7, 2019 at 2:33 PM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > On Mon, 2019-10-07 at 14:19 +0200, Dmitry Vyukov wrote: > > > On Mon, Oct 7, 2019 at 2:03 PM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > > My idea was just to always print "heap-out-of-bounds" and don't > > > differentiate if the size come from userspace or not. > > > > Got it. > > Would you have any other concern about this patch? > > > Last versions of the patch looked good to me except for the bug title. > The comment may also need some updating if you change the title. Updated, thanks again again. The patchsets help to produce KASAN report when size is negative numbers in memory operation function. It is helpful for programmer to solve the 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/ Walter Wu (2): kasan: detect invalid size in memory operation function kasan: add test for invalid size in memmove lib/test_kasan.c | 18 ++++++++++++++++++ mm/kasan/common.c | 13 ++++++++----- mm/kasan/generic.c | 5 +++++ mm/kasan/generic_report.c | 18 ++++++++++++++++++ mm/kasan/tags.c | 5 +++++ mm/kasan/tags_report.c | 17 +++++++++++++++++ 6 files changed, 71 insertions(+), 5 deletions(-) commit 1eb58140ac67debabdca705bafaadea934eb7820 Author: Walter-zh Wu <walter-zh.wu@xxxxxxxxxxxx> Date: Fri Oct 4 18:38:31 2019 +0800 kasan: detect negative size in memory operation function It is an undefined behavior to pass a negative numbers to memset()/memcpy()/memmove(), so need to be detected by KASAN. If size is negative numbers, then it has three reasons to be defined as heap-out-of-bounds bug type. 1) 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. 2) If KASAN has new bug type and user-space passes negative size, then there are duplicate reports. So don't produce new bug type in order to prevent duplicate reports by some systems (e.g. syzbot) to report the same bug twice. 3) When size is negative numbers, it may be passed from user-space. So we always print heap-out-of-bounds in order to prevent that kernel-space and user-space have the same bug but have duplicate reports. KASAN report: BUG: KASAN: heap-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 Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Reported -by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> diff --git a/mm/kasan/common.c b/mm/kasan/common.c index 6814d6d6a023..6ef0abd27f06 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -102,7 +102,8 @@ 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); } @@ -110,8 +111,9 @@ 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); } @@ -119,8 +121,9 @@ 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); } diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c index 616f9dd82d12..02148a317d27 100644 --- a/mm/kasan/generic.c +++ b/mm/kasan/generic.c @@ -173,6 +173,11 @@ static __always_inline bool check_memory_region_inline(unsigned long addr, if (unlikely(size == 0)) return true; + if (unlikely((long)size < 0)) { + kasan_report(addr, size, write, ret_ip); + return false; + } + if (unlikely((void *)addr < kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) { kasan_report(addr, size, write, ret_ip); diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c index 36c645939bc9..52a92c7db697 100644 --- a/mm/kasan/generic_report.c +++ b/mm/kasan/generic_report.c @@ -107,6 +107,24 @@ 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 negative numbers, then it has three reasons + * to be defined as heap-out-of-bounds bug type. + * 1) 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. + * 2) If KASAN has new bug type and user-space passes negative size, + * then there are duplicate reports. So don't produce new bug type + * in order to prevent duplicate reports by some systems + * (e.g. syzbot) to report the same bug twice. + * 3) When size is negative numbers, it may be passed from user-space. + * So we always print heap-out-of-bounds in order to prevent that + * kernel-space and user-space have the same bug but have duplicate + * reports. + */ + if ((long)info->access_size < 0) + return "heap-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/tags.c b/mm/kasan/tags.c index 0e987c9ca052..b829535a3ad7 100644 --- a/mm/kasan/tags.c +++ b/mm/kasan/tags.c @@ -86,6 +86,11 @@ bool check_memory_region(unsigned long addr, size_t size, bool write, if (unlikely(size == 0)) return true; + if (unlikely((long)size < 0)) { + kasan_report(addr, size, write, ret_ip); + return false; + } + tag = get_tag((const void *)addr); /* diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c index 969ae08f59d7..f7ae474aef3a 100644 --- a/mm/kasan/tags_report.c +++ b/mm/kasan/tags_report.c @@ -36,6 +36,24 @@ const char *get_bug_type(struct kasan_access_info *info) { + /* + * If access_size is negative numbers, then it has three reasons + * to be defined as heap-out-of-bounds bug type. + * 1) 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. + * 2) If KASAN has new bug type and user-space passes negative size, + * then there are duplicate reports. So don't produce new bug type + * in order to prevent duplicate reports by some systems + * (e.g. syzbot) to report the same bug twice. + * 3) When size is negative numbers, it may be passed from user-space. + * So we always print heap-out-of-bounds in order to prevent that + * kernel-space and user-space have the same bug but have duplicate + * reports. + */ + if ((long)info->access_size < 0) + return "heap-out-of-bounds"; + #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY struct kasan_alloc_meta *alloc_meta; struct kmem_cache *cache; commit fb5cf7bd16e939d1feef229af0211a8616c9ea03 Author: Walter-zh Wu <walter-zh.wu@xxxxxxxxxxxx> Date: Fri Oct 4 18:32:03 2019 +0800 kasan: add test for invalid size in memmove Test size is negative vaule in memmove in order to verify if it correctly get KASAN report. Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> diff --git a/lib/test_kasan.c b/lib/test_kasan.c index 49cc4d570a40..06942cf585cc 100644 --- a/lib/test_kasan.c +++ b/lib/test_kasan.c @@ -283,6 +283,23 @@ static noinline void __init kmalloc_oob_in_memset(void) kfree(ptr); } +static noinline void __init kmalloc_memmove_invalid_size(void) +{ + char *ptr; + size_t size = 64; + + pr_info("invalid size in memmove\n"); + ptr = kmalloc(size, GFP_KERNEL); + if (!ptr) { + pr_err("Allocation failed\n"); + return; + } + + memset((char *)ptr, 0, 64); + memmove((char *)ptr, (char *)ptr + 4, -2); + kfree(ptr); +} + static noinline void __init kmalloc_uaf(void) { char *ptr; @@ -773,6 +790,7 @@ static int __init kmalloc_tests_init(void) kmalloc_oob_memset_4(); kmalloc_oob_memset_8(); kmalloc_oob_memset_16(); + kmalloc_memmove_invalid_size(); kmalloc_uaf(); kmalloc_uaf_memset(); kmalloc_uaf2();
