| Message ID | 20210804090957.12393-2-Kuan-Ying.Lee@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kasan: reset tag when accessing invalid metadata | expand |
On Wed, Aug 4, 2021 at 11:10 AM Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote: > > Kmemleak need to scan kernel memory to check memory leak. > With hardware tag-based kasan enabled, when it scans on > the invalid slab and dereference, the issue will occur > as below. > > Hardware tag-based KASAN doesn't use compiler instrumentation, we > can not use kasan_disable_current() to ignore tag check. > > Based on the below report, there are 11 0xf7 granules, which amounts to > 176 bytes, and the object is allocated from the kmalloc-256 cache. So > when kmemleak accesses the last 256-176 bytes, it causes faults, as > those are marked with KASAN_KMALLOC_REDZONE == KASAN_TAG_INVALID == > 0xfe. > > Thus, we reset tags before accessing metadata to avoid from false positives. > > [ 151.905804] ================================================================== > [ 151.907120] BUG: KASAN: out-of-bounds in scan_block+0x58/0x170 > [ 151.908773] Read at addr f7ff0000c0074eb0 by task kmemleak/138 > [ 151.909656] Pointer tag: [f7], memory tag: [fe] > [ 151.910195] > [ 151.910876] CPU: 7 PID: 138 Comm: kmemleak Not tainted 5.14.0-rc2-00001-g8cae8cd89f05-dirty #134 > [ 151.912085] Hardware name: linux,dummy-virt (DT) > [ 151.912868] Call trace: > [ 151.913211] dump_backtrace+0x0/0x1b0 > [ 151.913796] show_stack+0x1c/0x30 > [ 151.914248] dump_stack_lvl+0x68/0x84 > [ 151.914778] print_address_description+0x7c/0x2b4 > [ 151.915340] kasan_report+0x138/0x38c > [ 151.915804] __do_kernel_fault+0x190/0x1c4 > [ 151.916386] do_tag_check_fault+0x78/0x90 > [ 151.916856] do_mem_abort+0x44/0xb4 > [ 151.917308] el1_abort+0x40/0x60 > [ 151.917754] el1h_64_sync_handler+0xb4/0xd0 > [ 151.918270] el1h_64_sync+0x78/0x7c > [ 151.918714] scan_block+0x58/0x170 > [ 151.919157] scan_gray_list+0xdc/0x1a0 > [ 151.919626] kmemleak_scan+0x2ac/0x560 > [ 151.920129] kmemleak_scan_thread+0xb0/0xe0 > [ 151.920635] kthread+0x154/0x160 > [ 151.921115] ret_from_fork+0x10/0x18 > [ 151.921717] > [ 151.922077] Allocated by task 0: > [ 151.922523] kasan_save_stack+0x2c/0x60 > [ 151.923099] __kasan_kmalloc+0xec/0x104 > [ 151.923502] __kmalloc+0x224/0x3c4 > [ 151.924172] __register_sysctl_paths+0x200/0x290 > [ 151.924709] register_sysctl_table+0x2c/0x40 > [ 151.925175] sysctl_init+0x20/0x34 > [ 151.925665] proc_sys_init+0x3c/0x48 > [ 151.926136] proc_root_init+0x80/0x9c > [ 151.926547] start_kernel+0x648/0x6a4 > [ 151.926987] __primary_switched+0xc0/0xc8 > [ 151.927557] > [ 151.927994] Freed by task 0: > [ 151.928340] kasan_save_stack+0x2c/0x60 > [ 151.928766] kasan_set_track+0x2c/0x40 > [ 151.929173] kasan_set_free_info+0x44/0x54 > [ 151.929568] ____kasan_slab_free.constprop.0+0x150/0x1b0 > [ 151.930063] __kasan_slab_free+0x14/0x20 > [ 151.930449] slab_free_freelist_hook+0xa4/0x1fc > [ 151.930924] kfree+0x1e8/0x30c > [ 151.931285] put_fs_context+0x124/0x220 > [ 151.931731] vfs_kern_mount.part.0+0x60/0xd4 > [ 151.932280] kern_mount+0x24/0x4c > [ 151.932686] bdev_cache_init+0x70/0x9c > [ 151.933122] vfs_caches_init+0xdc/0xf4 > [ 151.933578] start_kernel+0x638/0x6a4 > [ 151.934014] __primary_switched+0xc0/0xc8 > [ 151.934478] > [ 151.934757] The buggy address belongs to the object at ffff0000c0074e00 > [ 151.934757] which belongs to the cache kmalloc-256 of size 256 > [ 151.935744] The buggy address is located 176 bytes inside of > [ 151.935744] 256-byte region [ffff0000c0074e00, ffff0000c0074f00) > [ 151.936702] The buggy address belongs to the page: > [ 151.937378] page:(____ptrval____) refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x100074 > [ 151.938682] head:(____ptrval____) order:2 compound_mapcount:0 compound_pincount:0 > [ 151.939440] flags: 0xbfffc0000010200(slab|head|node=0|zone=2|lastcpupid=0xffff|kasantag=0x0) > [ 151.940886] raw: 0bfffc0000010200 0000000000000000 dead000000000122 f5ff0000c0002300 > [ 151.941634] raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000 > [ 151.942353] page dumped because: kasan: bad access detected > [ 151.942923] > [ 151.943214] Memory state around the buggy address: > [ 151.943896] ffff0000c0074c00: f0 f0 f0 f0 f0 f0 f0 f0 f0 fe fe fe fe fe fe fe > [ 151.944857] ffff0000c0074d00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe > [ 151.945892] >ffff0000c0074e00: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 fe fe fe fe fe > [ 151.946407] ^ > [ 151.946939] ffff0000c0074f00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe > [ 151.947445] ffff0000c0075000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 151.947999] ================================================================== > [ 151.948524] Disabling lock debugging due to kernel taint > [ 156.434569] kmemleak: 181 new suspected memory leaks (see /sys/kernel/debug/kmemleak) > > Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> > Acked-by: Catalin Marinas <catalin.marinas@arm.com> > Cc: Marco Elver <elver@google.com> > Cc: Andrey Konovalov <andreyknvl@gmail.com> > --- > mm/kmemleak.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > index 228a2fbe0657..73d46d16d575 100644 > --- a/mm/kmemleak.c > +++ b/mm/kmemleak.c > @@ -290,7 +290,7 @@ static void hex_dump_object(struct seq_file *seq, > warn_or_seq_printf(seq, " hex dump (first %zu bytes):\n", len); > kasan_disable_current(); > warn_or_seq_hex_dump(seq, DUMP_PREFIX_NONE, HEX_ROW_SIZE, > - HEX_GROUP_SIZE, ptr, len, HEX_ASCII); > + HEX_GROUP_SIZE, kasan_reset_tag((void *)ptr), len, HEX_ASCII); > kasan_enable_current(); > } > > @@ -1171,7 +1171,7 @@ static bool update_checksum(struct kmemleak_object *object) > > kasan_disable_current(); > kcsan_disable_current(); > - object->checksum = crc32(0, (void *)object->pointer, object->size); > + object->checksum = crc32(0, kasan_reset_tag((void *)object->pointer), object->size); > kasan_enable_current(); > kcsan_enable_current(); > > @@ -1246,7 +1246,7 @@ static void scan_block(void *_start, void *_end, > break; > > kasan_disable_current(); > - pointer = *ptr; > + pointer = *(unsigned long *)kasan_reset_tag((void *)ptr); > kasan_enable_current(); > > untagged_ptr = (unsigned long)kasan_reset_tag((void *)pointer); > -- > 2.18.0 > Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 228a2fbe0657..73d46d16d575 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -290,7 +290,7 @@ static void hex_dump_object(struct seq_file *seq, warn_or_seq_printf(seq, " hex dump (first %zu bytes):\n", len); kasan_disable_current(); warn_or_seq_hex_dump(seq, DUMP_PREFIX_NONE, HEX_ROW_SIZE, - HEX_GROUP_SIZE, ptr, len, HEX_ASCII); + HEX_GROUP_SIZE, kasan_reset_tag((void *)ptr), len, HEX_ASCII); kasan_enable_current(); } @@ -1171,7 +1171,7 @@ static bool update_checksum(struct kmemleak_object *object) kasan_disable_current(); kcsan_disable_current(); - object->checksum = crc32(0, (void *)object->pointer, object->size); + object->checksum = crc32(0, kasan_reset_tag((void *)object->pointer), object->size); kasan_enable_current(); kcsan_enable_current(); @@ -1246,7 +1246,7 @@ static void scan_block(void *_start, void *_end, break; kasan_disable_current(); - pointer = *ptr; + pointer = *(unsigned long *)kasan_reset_tag((void *)ptr); kasan_enable_current(); untagged_ptr = (unsigned long)kasan_reset_tag((void *)pointer);