KASAN: use-after-free Read in blkcg_print_stat

Status: auto-closed as invalid on 2019/10/25 08:44
Subsystems: block cgroups
[Documentation on labels]
Reported-by: syzbot+18a2377b010d621c950e@syzkaller.appspotmail.com
First crash: 2675d, last: 2618d
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
KASAN: use-after-free Read in blkcg_print_stat 0 (1) 2019/04/14 16:48
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 KASAN: use-after-free Read in blkcg_print_stat 19 1 2457d 2457d 0/1 auto-closed as invalid on 2020/03/17 10:06
upstream KASAN: use-after-free Read in blkcg_print_stat (2) block cgroups 19 1 2459d 2457d 0/29 auto-closed as invalid on 2020/03/16 06:09

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in string_nocheck+0x1e4/0x210 lib/vsprintf.c:605
Read of size 1 at addr ffff8880a0fb6f00 by task syz-executor.5/9374

CPU: 1 PID: 9374 Comm: syz-executor.5 Not tainted 5.2.0-rc4 #44
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:188
 __kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
 kasan_report+0x12/0x20 mm/kasan/common.c:614
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:129
 string_nocheck+0x1e4/0x210 lib/vsprintf.c:605
 string+0xed/0x100 lib/vsprintf.c:668
 vsnprintf+0x97b/0x19a0 lib/vsprintf.c:2503
 vscnprintf lib/vsprintf.c:2606 [inline]
 scnprintf+0xbb/0x140 lib/vsprintf.c:2660
 blkcg_print_stat+0x1f2/0xb30 block/blk-cgroup.c:958
 cgroup_seqfile_show+0x1ae/0x310 kernel/cgroup/cgroup.c:3783
 kernfs_seq_show+0x14f/0x1b0 fs/kernfs/file.c:167
 seq_read+0x4ca/0x1110 fs/seq_file.c:229
 kernfs_fop_read+0xed/0x560 fs/kernfs/file.c:251
 do_loop_readv_writev fs/read_write.c:714 [inline]
 do_loop_readv_writev fs/read_write.c:701 [inline]
 do_iter_read+0x4a4/0x660 fs/read_write.c:935
 vfs_readv+0xf0/0x160 fs/read_write.c:997
 do_readv+0x15b/0x330 fs/read_write.c:1034
 __do_sys_readv fs/read_write.c:1125 [inline]
 __se_sys_readv fs/read_write.c:1122 [inline]
 __x64_sys_readv+0x75/0xb0 fs/read_write.c:1122
 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459279
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f0e27f58c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000013
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459279
RDX: 000000000000017c RSI: 00000000200002c0 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f0e27f596d4
R13: 00000000004c6392 R14: 00000000004db1c0 R15: 00000000ffffffff

Allocated by task 9703:
 save_stack+0x23/0x90 mm/kasan/common.c:71
 set_track mm/kasan/common.c:79 [inline]
 __kasan_kmalloc mm/kasan/common.c:489 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:462
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:503
 __do_kmalloc mm/slab.c:3660 [inline]
 __kmalloc_track_caller+0x158/0x740 mm/slab.c:3675
 kvasprintf+0xc8/0x170 lib/kasprintf.c:25
 kvasprintf_const+0x65/0x190 lib/kasprintf.c:49
 kobject_set_name_vargs+0x5b/0x150 lib/kobject.c:289
 device_create_groups_vargs+0x1bb/0x270 drivers/base/core.c:2712
 device_create_vargs+0x45/0x60 drivers/base/core.c:2756
 bdi_register_va.part.0+0x38/0x740 mm/backing-dev.c:883
 bdi_register_va mm/backing-dev.c:911 [inline]
 bdi_register+0x12a/0x140 mm/backing-dev.c:908
 bdi_register_owner+0x6a/0x110 mm/backing-dev.c:918
 __device_add_disk+0xdb1/0x11c0 block/genhd.c:730
 device_add_disk+0x2b/0x40 block/genhd.c:754
 add_disk include/linux/genhd.h:429 [inline]
 loop_add+0x635/0x8d0 drivers/block/loop.c:2056
 loop_probe+0x161/0x1a0 drivers/block/loop.c:2128
 kobj_lookup+0x260/0x460 drivers/base/map.c:124
 get_gendisk+0x4d/0x390 block/genhd.c:869
 bdev_get_gendisk fs/block_dev.c:1112 [inline]
 __blkdev_get+0x457/0x1660 fs/block_dev.c:1505
 blkdev_get+0xc4/0x990 fs/block_dev.c:1664
 blkdev_open+0x205/0x290 fs/block_dev.c:1822
 do_dentry_open+0x4df/0x1250 fs/open.c:778
 vfs_open+0xa0/0xd0 fs/open.c:887
 do_last fs/namei.c:3416 [inline]
 path_openat+0x10e9/0x46d0 fs/namei.c:3533
 do_filp_open+0x1a1/0x280 fs/namei.c:3563
 do_sys_open+0x3fe/0x5d0 fs/open.c:1070
 __do_sys_open fs/open.c:1088 [inline]
 __se_sys_open fs/open.c:1083 [inline]
 __x64_sys_open+0x7e/0xc0 fs/open.c:1083
 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 9383:
 save_stack+0x23/0x90 mm/kasan/common.c:71
 set_track mm/kasan/common.c:79 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:451
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:459
 __cache_free mm/slab.c:3432 [inline]
 kfree+0xcf/0x220 mm/slab.c:3755
 kfree_const+0x59/0x70 mm/util.c:32
 kobject_cleanup lib/kobject.c:697 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put.cold+0x2b3/0x2e6 lib/kobject.c:737
 put_device drivers/base/core.c:2210 [inline]
 device_unregister+0x28/0x40 drivers/base/core.c:2307
 bdi_unregister+0x41c/0x5e0 mm/backing-dev.c:950
 del_gendisk+0x896/0xb30 block/genhd.c:801
 loop_remove+0x3c/0xd0 drivers/block/loop.c:2074
 loop_control_ioctl drivers/block/loop.c:2173 [inline]
 loop_control_ioctl+0x320/0x360 drivers/block/loop.c:2139
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880a0fb6f00
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
 32-byte region [ffff8880a0fb6f00, ffff8880a0fb6f20)
The buggy address belongs to the page:
page:ffffea000283ed80 refcount:1 mapcount:0 mapping:ffff8880aa4001c0 index:0xffff8880a0fb6fc1
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002a0c608 ffffea000280e488 ffff8880aa4001c0
raw: ffff8880a0fb6fc1 ffff8880a0fb6000 000000010000003a 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a0fb6e00: fb fb fb fb fc fc fc fc 00 00 00 00 fc fc fc fc
 ffff8880a0fb6e80: fb fb fb fb fc fc fc fc 00 00 fc fc fc fc fc fc
>ffff8880a0fb6f00: fb fb fb fb fc fc fc fc 00 00 fc fc fc fc fc fc
                   ^
 ffff8880a0fb6f80: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a0fb7000: 00 00 00 00 00 fc fc 00 00 00 00 00 fc fc 00 00
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2019/06/10 13:39 upstream d1fdb6d8f6a4 0159583c .config console log report ci-upstream-kasan-gce
2019/04/14 12:21 upstream 4443f8e6ac77 505ab413 .config console log report ci-upstream-kasan-gce
* Struck through repros no longer work on HEAD.