On Fri, Oct 4, 2019 at 2:05 PM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > 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"; wait, no :) I meant we change it to heap-out-of-bounds and explain why we are saying this is a heap-out-of-bounds. The current comment effectively says we are doing non useful thing for no reason, it does not eliminate any of my questions as a reader of this code :) > + > #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();
