On Fri, 2019-10-04 at 15:52 +0200, Dmitry Vyukov wrote: > 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 :) > Ok, the current comment may not enough to be understood why we use OOB to represent size<0 bug. We can modify it as below :) If access_size < 0, then it has two reasons to be defined as out-of-bounds. 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) Don't generate new bug type in order to prevent duplicate reports by some systems, e.g. syzbot." > > > > > + > > #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();
