Re: KASAN: use-after-free Read in corrupted

[Dmitry Vyukov]

On Sun, May 13, 2018 at 10:56 AM, syzbot
<syzbot+3417712847e7219a60ee@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    427fbe89261d Merge branch 'next' of git://git.kernel.org/p..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=148eb017800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=fcce42b221691ff9
> dashboard link: https://syzkaller.appspot.com/bug?extid=3417712847e7219a60ee
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1770c477800000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14ecdbc7800000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+3417712847e7219a60ee@xxxxxxxxxxxxxxxxxxxxxxxxx

Tetsuo,

This looks very similar to "KASAN: use-after-free Read in fuse_kill_sb_blk":
https://groups.google.com/d/msg/syzkaller-bugs/4C4oiBX8vZ0/0NTQRcUYBgAJ

which you fixed with "fuse: don't keep dead fuse_conn at fuse_fill_super().":
https://groups.google.com/d/msg/syzkaller-bugs/4C4oiBX8vZ0/W6pi8NdbBgAJ

However, here we have use-after-free in fuse_kill_sb_anon instead of
use_kill_sb_blk. Do you think your patch will fix this as well?



> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> CPU: 0 PID: 4564 Comm: syz-executor214 Not tainted 4.17.0-rc4+ #44
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> ==================================================================
> Call Trace:
> BUG: KASAN: use-after-free in __lock_acquire+0x3888/0x5140
> kernel/locking/lockdep.c:3310
> Read of size 8 at addr ffff8801d8d69088 by task syz-executor214/4551
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
>
>  fail_dump lib/fault-inject.c:51 [inline]
>  should_fail.cold.4+0xa/0x1a lib/fault-inject.c:149
>  __should_failslab+0x124/0x180 mm/failslab.c:32
>  should_failslab+0x9/0x14 mm/slab_common.c:1522
>  slab_pre_alloc_hook mm/slab.h:423 [inline]
>  slab_alloc mm/slab.c:3378 [inline]
>  kmem_cache_alloc+0x2af/0x760 mm/slab.c:3552
>  __d_alloc+0xc0/0xd30 fs/dcache.c:1638
>  d_alloc_anon fs/dcache.c:1742 [inline]
>  d_make_root+0x42/0x90 fs/dcache.c:1934
>  fuse_fill_super+0x120e/0x1e20 fs/fuse/inode.c:1131
>  mount_nodev+0x6b/0x110 fs/super.c:1210
>  fuse_mount+0x2c/0x40 fs/fuse/inode.c:1192
>  mount_fs+0xae/0x328 fs/super.c:1267
>  vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037
>  vfs_kern_mount fs/namespace.c:1027 [inline]
>  do_new_mount fs/namespace.c:2518 [inline]
>  do_mount+0x564/0x3070 fs/namespace.c:2848
>  ksys_mount+0x12d/0x140 fs/namespace.c:3064
>  __do_sys_mount fs/namespace.c:3078 [inline]
>  __se_sys_mount fs/namespace.c:3075 [inline]
>  __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x447cb9
> RSP: 002b:00007f7a75bca918 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000447cb9
> RDX: 00000000004b08d6 RSI: 0000000020000340 RDI: 00000000004c7485
> RBP: 000000000000a001 R08: 00007f7a75bca930 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> CPU: 1 PID: 4551 Comm: syz-executor214 Not tainted 4.17.0-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+0x1b9/0x294 lib/dump_stack.c:113
> FAULT_INJECTION: forcing a failure.
> name failslab, interval 1, probability 0, space 0, times 0
>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>  __lock_acquire+0x3888/0x5140 kernel/locking/lockdep.c:3310
>  lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920
>  down_write+0x87/0x120 kernel/locking/rwsem.c:70
>  fuse_kill_sb_anon+0x50/0xb0 fs/fuse/inode.c:1200
>  deactivate_locked_super+0x97/0x100 fs/super.c:316
>  mount_nodev+0xfa/0x110 fs/super.c:1212
>  fuse_mount+0x2c/0x40 fs/fuse/inode.c:1192
>  mount_fs+0xae/0x328 fs/super.c:1267
>  vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037
>  vfs_kern_mount fs/namespace.c:1027 [inline]
>  do_new_mount fs/namespace.c:2518 [inline]
>  do_mount+0x564/0x3070 fs/namespace.c:2848
>  ksys_mount+0x12d/0x140 fs/namespace.c:3064
>  __do_sys_mount fs/namespace.c:3078 [inline]
>  __se_sys_mount fs/namespace.c:3075 [inline]
>  __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x447cb9
> RSP: 002b:00007f7a75bca918 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000447cb9
> RDX: 00000000004b08d6 RSI: 0000000020000340 RDI: 00000000004c7485
> RBP: 000000000000a001 R08: 00007f7a75bca930 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>
> CPU: 0 PID: 4580 Comm: syz-executor214 Not tainted 4.17.0-rc4+ #44
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Allocated by task 4551:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
> Call Trace:
>  set_track mm/kasan/kasan.c:460 [inline]
>  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
>  kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
>  kmalloc include/linux/slab.h:512 [inline]
>  fuse_fill_super+0xc92/0x1e20 fs/fuse/inode.c:1096
>  mount_nodev+0x6b/0x110 fs/super.c:1210
>  fuse_mount+0x2c/0x40 fs/fuse/inode.c:1192
>  mount_fs+0xae/0x328 fs/super.c:1267
>  vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037
>  vfs_kern_mount fs/namespace.c:1027 [inline]
>  do_new_mount fs/namespace.c:2518 [inline]
>  do_mount+0x564/0x3070 fs/namespace.c:2848
>  fail_dump lib/fault-inject.c:51 [inline]
>  should_fail.cold.4+0xa/0x1a lib/fault-inject.c:149
>  ksys_mount+0x12d/0x140 fs/namespace.c:3064
>  __do_sys_mount fs/namespace.c:3078 [inline]
>  __se_sys_mount fs/namespace.c:3075 [inline]
>  __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 8:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
>  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
>  __cache_free mm/slab.c:3498 [inline]
>  kfree+0xd9/0x260 mm/slab.c:3813
>  __rcu_reclaim kernel/rcu/rcu.h:173 [inline]
>  rcu_do_batch kernel/rcu/tree.c:2675 [inline]
>  invoke_rcu_callbacks kernel/rcu/tree.c:2930 [inline]
>  __rcu_process_callbacks kernel/rcu/tree.c:2897 [inline]
>  rcu_process_callbacks+0xa69/0x15f0 kernel/rcu/tree.c:2914
>  __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285
>
> The buggy address belongs to the object at ffff8801d8d68dc0
>  which belongs to the cache kmalloc-1024 of size 1024
> The buggy address is located 712 bytes inside of
>  1024-byte region [ffff8801d8d68dc0, ffff8801d8d691c0)
> The buggy address belongs to the page:
> page:ffffea0007635a00 count:1 mapcount:0 mapping:ffff8801d8d68040 index:0x0
>  compound_mapcount: 0
> flags: 0x2fffc0000008100(slab|head)
>  __should_failslab+0x124/0x180 mm/failslab.c:32
> raw: 02fffc0000008100 ffff8801d8d68040 0000000000000000 0000000100000007
>  should_failslab+0x9/0x14 mm/slab_common.c:1522
> raw: ffffea00076407a0 ffffea00076335a0 ffff8801da800ac0 0000000000000000
>  slab_pre_alloc_hook mm/slab.h:423 [inline]
>  slab_alloc mm/slab.c:3378 [inline]
>  kmem_cache_alloc+0x2af/0x760 mm/slab.c:3552
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801d8d68f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801d8d69000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>
>> ffff8801d8d69080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>
>  __d_alloc+0xc0/0xd30 fs/dcache.c:1638
>                       ^
>  ffff8801d8d69100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801d8d69180: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
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