On Fri, 2019-10-04 at 11:54 +0200, Dmitry Vyukov wrote: > > > "out-of-bounds" is the _least_ frequent KASAN bug type. So saying > > > "out-of-bounds" has downsides of both approaches and won't prevent > > > duplicate reports by syzbot... > > > > > maybe i should add your comment into the comment in get_bug_type? > > Yes, that's exactly what I meant above: > > "I would change get_bug_type() to return "slab-out-of-bounds" (as the > most common OOB) in such case (with a comment)." > > ;) The patchset help to produce KASAN report when size is negative size in memory operation function. It is helpful for programmer to solve the undefined behavior issue. Patch 1 based on Dmitry's suggestion and review, 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 | 10 ++++++++++ mm/kasan/tags.c | 5 +++++ mm/kasan/tags_report.c | 10 ++++++++++ 6 files changed, 56 insertions(+), 5 deletions(-) commit 0bc50c759a425fa0aafb7ef623aa1598b3542c67 Author: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Date: Fri Oct 4 18:38:31 2019 +0800 kasan: detect invalid size in memory operation function It is an undefined behavior to pass a negative value to memset()/memcpy()/memmove() , so need to be detected by KASAN. If size is negative value, then it will be larger than ULONG_MAX/2, so that we will qualify as out-of-bounds issue. KASAN report: 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 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..23951a453681 100644 --- a/mm/kasan/generic_report.c +++ b/mm/kasan/generic_report.c @@ -107,6 +107,16 @@ 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 < 0, then it will be larger than ULONG_MAX/2, + * so that this can qualify as out-of-bounds. + * out-of-bounds is the _least_ frequent KASAN bug type. So saying + * out-of-bounds has downsides of both approaches and won't prevent + * duplicate reports by syzbot. + */ + if ((long)info->access_size < 0) + 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/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..19b9e364b397 100644 --- a/mm/kasan/tags_report.c +++ b/mm/kasan/tags_report.c @@ -36,6 +36,16 @@ const char *get_bug_type(struct kasan_access_info *info) { + /* + * if access_size < 0, then it will be larger than ULONG_MAX/2, + * so that this can qualify as out-of-bounds. + * out-of-bounds is the _least_ frequent KASAN bug type. So saying + * out-of-bounds has downsides of both approaches and won't prevent + * duplicate reports by syzbot. + */ + if ((long)info->access_size < 0) + return "out-of-bounds"; + #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY struct kasan_alloc_meta *alloc_meta; struct kmem_cache *cache; commit fb5cf7bd16e939d1feef229af0211a8616c9ea03 Author: Walter 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 produce 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();
