On Mon, Oct 7, 2019 at 11:50 AM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > On Mon, 2019-10-07 at 17:28 +0800, Walter Wu wrote: > > On Mon, 2019-10-07 at 11:10 +0200, Dmitry Vyukov wrote: > > > On Mon, Oct 7, 2019 at 11:03 AM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > > > > > > > On Mon, 2019-10-07 at 10:54 +0200, Dmitry Vyukov wrote: > > > > > On Mon, Oct 7, 2019 at 10:52 AM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > > > > > > > > > > > On Mon, 2019-10-07 at 10:24 +0200, Dmitry Vyukov wrote: > > > > > > > On Mon, Oct 7, 2019 at 10:18 AM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > > > > > > > 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 | 12 ++++++++++++ > > > > > > > > mm/kasan/tags.c | 5 +++++ > > > > > > > > mm/kasan/tags_report.c | 12 ++++++++++++ > > > > > > > > 6 files changed, 60 insertions(+), 5 deletions(-) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > commit 5b3b68660b3d420fd2bd792f2d9fd3ccb8877ef7 > > > > > > > > Author: Walter-zh 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 numbers to > > > > > > > > memset()/memcpy()/memmove() > > > > > > > > , so need to be detected by KASAN. > > > > > > > > > > > > > > > > If size is negative numbers, then it has two reasons to be defined > > > > > > > > as 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) Don't generate new bug type in order to prevent duplicate reports > > > > > > > > by > > > > > > > > some systems, e.g. syzbot. > > > > > > > > > > > > > > > > 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..ed0eb94cb811 100644 > > > > > > > > --- a/mm/kasan/generic_report.c > > > > > > > > +++ b/mm/kasan/generic_report.c > > > > > > > > @@ -107,6 +107,18 @@ 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 two reasons > > > > > > > > + * to be defined as 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) Don't generate new bug type in order to prevent duplicate > > > > > > > > reports > > > > > > > > + * by some systems, e.g. syzbot. > > > > > > > > + */ > > > > > > > > + if ((long)info->access_size < 0) > > > > > > > > + return "out-of-bounds"; > > > > > > > > > > > > > > "out-of-bounds" is the _least_ frequent KASAN bug type. It won't > > > > > > > prevent duplicates. "heap-out-of-bounds" is the frequent one. > > > > > > > > > > > > > > > > > > /* > > > > > > * If access_size is negative numbers, then it has two reasons > > > > > > * to be defined as 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) Don't generate new bug type in order to prevent duplicate > > > > > > reports > > > > > > * by some systems, e.g. syzbot. "out-of-bounds" is the _least_ > > > > > > frequent KASAN bug type. > > > > > > * It won't prevent duplicates. "heap-out-of-bounds" is the > > > > > > frequent one. > > > > > > */ > > > > > > > > > > > > We directly add it into the comment. > > > > > > > > > > > > > > > OK, let's start from the beginning: why do you return "out-of-bounds" here? > > > > > > > > > Uh, comment 1 and 2 should explain it. :) > > > > > > The comment says it will cause duplicate reports. It does not explain > > > why you want syzbot to produce duplicate reports and spam kernel > > > developers... So why do you want that? > > > > > We don't generate new bug type in order to prevent duplicate by some > > systems, e.g. syzbot. Is it right? If yes, then it should not have > > duplicate report. > > > Sorry, because we don't generate new bug type. it should be duplicate > report(only one report which may be oob or size invlid), > the duplicate report goal is that invalid size is oob issue, too. > > I would not introduce a new bug type. > These are parsed and used by some systems, e.g. syzbot. If size is > user-controllable, then a new bug type for this will mean 2 bug > reports. To prevent duplicates, the new crash title must not just match _any_ crash title that kernel can potentially produce. It must match exactly the crash that kernel produces for this bug on other input data. Consider, userspace passes size=123, KASAN produces "heap-out-of-bounds in foo". Now userspace passes size=-1 and KASAN produces "invalid-size in foo". This will be a duplicate bug report. Now if KASAN will produce "out-of-bounds in foo", it will also lead to a duplicate report. Only iff KASAN will produce "heap-out-of-bounds in foo" for size=-1, it will not lead to a duplicate report.
