On Thu, Oct 3, 2019 at 3:51 PM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote:> > how about this? > > commit fd64691026e7ccb8d2946d0804b0621ac177df38 > Author: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> > Date: Fri Sep 27 09:54:18 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. > > KASAN report: > > BUG: KASAN: invalid size 18446744073709551614 in > kmalloc_memmove_invalid_size+0x70/0xa0 > > CPU: 1 PID: 91 Comm: cat Not tainted > 5.3.0-rc1ajb-00001-g31943bbc21ce-dirty #7 > Hardware name: linux,dummy-virt (DT) > Call trace: > dump_backtrace+0x0/0x278 > show_stack+0x14/0x20 > dump_stack+0x108/0x15c > print_address_description+0x64/0x368 > __kasan_report+0x108/0x1a4 > kasan_report+0xc/0x18 > check_memory_region+0x15c/0x1b8 > 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> > > diff --git a/lib/test_kasan.c b/lib/test_kasan.c > index b63b367a94e8..e4e517a51860 100644 > --- a/lib/test_kasan.c > +++ b/lib/test_kasan.c > @@ -280,6 +280,23 @@ 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; > @@ -734,6 +751,7 @@ 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(); > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index 2277b82902d8..5fd377af7457 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; Overall approach looks good to me. A good question is what we should return here. All bets are off after a report, but we still try to "minimize damage". One may argue for returning addr here and in other functions. But the more I think about this, the more I think it does not matter. > return __memset(addr, c, len); > } > @@ -110,7 +111,8 @@ 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_); > + if(!check_memory_region((unsigned long)src, len, false, _RET_IP_)) > + return NULL; > check_memory_region((unsigned long)dest, len, true, _RET_IP_); > > return __memmove(dest, src, len); > @@ -119,7 +121,8 @@ 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_); > + if(!check_memory_region((unsigned long)src, len, false, _RET_IP_)) > + return NULL; > check_memory_region((unsigned long)dest, len, true, _RET_IP_); > > 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/report.c b/mm/kasan/report.c > index 0e5f965f1882..0cd317ef30f5 100644 > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -68,11 +68,16 @@ __setup("kasan_multi_shot", kasan_set_multi_shot); > > static void print_error_description(struct kasan_access_info *info) > { > - pr_err("BUG: KASAN: %s in %pS\n", > - get_bug_type(info), (void *)info->ip); > - pr_err("%s of size %zu at addr %px by task %s/%d\n", > - info->is_write ? "Write" : "Read", info->access_size, > - info->access_addr, current->comm, task_pid_nr(current)); > + if ((long)info->access_size < 0) { > + pr_err("BUG: KASAN: invalid size %zu in %pS\n", > + info->access_size, (void *)info->ip); 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. It also won't harm to print Read/Write, definitely the address, so no reason to special case this out of a dozen of report formats. This can qualify as out-of-bounds (definitely will cross some bounds!), so I would change get_bug_type() to return "slab-out-of-bounds" (as the most common OOB) in such case (with a comment). > + } else { > + pr_err("BUG: KASAN: %s in %pS\n", > + get_bug_type(info), (void *)info->ip); > + pr_err("%s of size %zu at addr %px by task %s/%d\n", > + info->is_write ? "Write" : "Read", info->access_size, > + info->access_addr, current->comm, task_pid_nr(current)); > + } > } > > static DEFINE_SPINLOCK(report_lock); > 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); > > /* > > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/1570110681.19702.64.camel%40mtksdccf07.
