Re: kernel BUG in btrfs_free_tree_block

[Qu Wenruo]

On 2021/9/14 上午10:07, Hao Sun wrote:
> Hello,
>
> When using Healer to fuzz the latest Linux kernel, the following crash
> was triggered.
>
> HEAD commit: 6880fa6c5660 Linux 5.15-rc1
> git tree: upstream
> console output:
> https://drive.google.com/file/d/1Dj7_zR7EzzSb0ba9M7QS43O3jrWBdaGW/view?usp=sharing
> kernel config: https://drive.google.com/file/d/1rUzyMbe5vcs6khA3tL9EHTLJvsUdWcgB/view?usp=sharing
> C reproducer: https://drive.google.com/file/d/19Of7kky0AvoVCnDh45TfsFDgQ_HBZW67/view?usp=sharing
> Syzlang reproducer:
> https://drive.google.com/file/d/10Ltk6J-pt41zI95k8B5gI-sZBZjI4Wyh/view?usp=sharing
>
> If you fix this issue, please add the following tag to the commit:
> Reported-by: Hao Sun <sunhao.th@xxxxxxxxx>
>
> loop13: detected capacity change from 0 to 32768
> BTRFS: device fsid 88a22be4-8cb5-4ed2-8c2d-1957ce391952 devid 1
> transid 7 /dev/loop13 scanned by syz-executor (7196)
> BTRFS info (device loop13): disk space caching is enabled
> BTRFS info (device loop13): has skinny extents
> BTRFS info (device loop13): enabling ssd optimizations
> FAULT_INJECTION: forcing a failure.
> name failslab, interval 1, probability 0, space 0, times 1
> CPU: 3 PID: 7196 Comm: syz-executor Not tainted 5.15.0-rc1 #16
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
> Call Trace:
>   __dump_stack lib/dump_stack.c:88 [inline]
>   dump_stack_lvl+0x8d/0xcf lib/dump_stack.c:106
>   fail_dump lib/fault-inject.c:52 [inline]
>   should_fail+0x13c/0x160 lib/fault-inject.c:146
>   should_failslab+0x5/0x10 mm/slab_common.c:1328
>   slab_pre_alloc_hook.constprop.99+0x4e/0xc0 mm/slab.h:494
>   slab_alloc_node mm/slub.c:3120 [inline]
>   slab_alloc mm/slub.c:3214 [inline]
>   kmem_cache_alloc+0x44/0x280 mm/slub.c:3219
>   btrfs_add_delayed_tree_ref+0xa1/0x580 fs/btrfs/delayed-ref.c:913
>   btrfs_free_tree_block+0x14c/0x440 fs/btrfs/extent-tree.c:3296

This is a direct BUG_ON() handling -ENOMEM.

For this particular case, it looks like aborting transaction is the only
solution, or we will need to change tons of code to accept an error
return value.


And a quick grep would show at least 21 such errors. ("BUG_ON.*ENOMEM")

Maybe it's time for us to start a new round of BUG_ON() hunt.

Thanks,
Qu

>   __btrfs_cow_block+0x5f6/0x7d0 fs/btrfs/ctree.c:465
>   btrfs_cow_block+0x12a/0x300 fs/btrfs/ctree.c:570
>   btrfs_search_slot+0x6b0/0xee0 fs/btrfs/ctree.c:1768
>   btrfs_insert_empty_items+0x80/0xf0 fs/btrfs/ctree.c:3905
>   btrfs_new_inode+0x311/0xa60 fs/btrfs/inode.c:6530
>   btrfs_create+0x12b/0x270 fs/btrfs/inode.c:6783
>   lookup_open+0x660/0x780 fs/namei.c:3282
>   open_last_lookups fs/namei.c:3352 [inline]
>   path_openat+0x465/0xe20 fs/namei.c:3557
>   do_filp_open+0xe3/0x170 fs/namei.c:3588
>   do_sys_openat2+0x357/0x4a0 fs/open.c:1200
>   do_sys_open+0x87/0xd0 fs/open.c:1216
>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>   do_syscall_64+0x34/0xb0 arch/x86/entry/common.c:80
>   entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x46ae99
> Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f0ffa345c48 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
> RAX: ffffffffffffffda RBX: 000000000078c0a0 RCX: 000000000046ae99
> RDX: 0000000000000000 RSI: 00000000000000a1 RDI: 0000000020005800
> RBP: 00007f0ffa345c80 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000001d
> R13: 0000000000000000 R14: 000000000078c0a0 R15: 00007ffd3f5c1ed0
> ------------[ cut here ]------------
> kernel BUG at fs/btrfs/extent-tree.c:3297!
> invalid opcode: 0000 [#1] PREEMPT SMP
> CPU: 3 PID: 7196 Comm: syz-executor Not tainted 5.15.0-rc1 #16
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
> RIP: 0010:btrfs_free_tree_block+0x159/0x440 fs/btrfs/extent-tree.c:3297
> Code: 5b 5d 41 5c 41 5d 41 5e 41 5f c3 e8 81 9d 4d ff 31 d2 4c 89 e7
> 48 89 e6 e8 e4 96 09 00 85 c0 0f 84 68 ff ff ff e8 67 9d 4d ff <0f> 0b
> e8 60 9d 4d ff 48 83 bd df 01 00 00 fa 74 27 e8 51 9d 4d ff
> RSP: 0018:ffffc9000528f7c8 EFLAGS: 00010246
> RAX: 0000000000040000 RBX: ffff888104ba4d80 RCX: ffffc9000125d000
> RDX: 0000000000040000 RSI: ffffffff81e9f499 RDI: ffffffff853cbec6
> RBP: ffff888103c67000 R08: 0000000000000068 R09: 0000000000000001
> R10: ffffc9000528f638 R11: 0000000000000005 R12: ffff888106374000
> R13: 0000000000000001 R14: ffff88810965c000 R15: 0000000000000000
> FS:  00007f0ffa346700(0000) GS:ffff88813dd00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000788000 CR3: 000000001aa9c000 CR4: 0000000000750ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> PKRU: 55555554
> Call Trace:
>   __btrfs_cow_block+0x5f6/0x7d0 fs/btrfs/ctree.c:465
>   btrfs_cow_block+0x12a/0x300 fs/btrfs/ctree.c:570
>   btrfs_search_slot+0x6b0/0xee0 fs/btrfs/ctree.c:1768
>   btrfs_insert_empty_items+0x80/0xf0 fs/btrfs/ctree.c:3905
>   btrfs_new_inode+0x311/0xa60 fs/btrfs/inode.c:6530
>   btrfs_create+0x12b/0x270 fs/btrfs/inode.c:6783
>   lookup_open+0x660/0x780 fs/namei.c:3282
>   open_last_lookups fs/namei.c:3352 [inline]
>   path_openat+0x465/0xe20 fs/namei.c:3557
>   do_filp_open+0xe3/0x170 fs/namei.c:3588
>   do_sys_openat2+0x357/0x4a0 fs/open.c:1200
>   do_sys_open+0x87/0xd0 fs/open.c:1216
>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>   do_syscall_64+0x34/0xb0 arch/x86/entry/common.c:80
>   entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x46ae99
> Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f0ffa345c48 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
> RAX: ffffffffffffffda RBX: 000000000078c0a0 RCX: 000000000046ae99
> RDX: 0000000000000000 RSI: 00000000000000a1 RDI: 0000000020005800
> RBP: 00007f0ffa345c80 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000001d
> R13: 0000000000000000 R14: 000000000078c0a0 R15: 00007ffd3f5c1ed0
> Modules linked in:
> Dumping ftrace buffer:
>     (ftrace buffer empty)
> ---[ end trace 917bc653bd051886 ]---
> RIP: 0010:btrfs_free_tree_block+0x159/0x440 fs/btrfs/extent-tree.c:3297
> Code: 5b 5d 41 5c 41 5d 41 5e 41 5f c3 e8 81 9d 4d ff 31 d2 4c 89 e7
> 48 89 e6 e8 e4 96 09 00 85 c0 0f 84 68 ff ff ff e8 67 9d 4d ff <0f> 0b
> e8 60 9d 4d ff 48 83 bd df 01 00 00 fa 74 27 e8 51 9d 4d ff
> RSP: 0018:ffffc9000528f7c8 EFLAGS: 00010246
> RAX: 0000000000040000 RBX: ffff888104ba4d80 RCX: ffffc9000125d000
> RDX: 0000000000040000 RSI: ffffffff81e9f499 RDI: ffffffff853cbec6
> RBP: ffff888103c67000 R08: 0000000000000068 R09: 0000000000000001
> R10: ffffc9000528f638 R11: 0000000000000005 R12: ffff888106374000
> R13: 0000000000000001 R14: ffff88810965c000 R15: 0000000000000000
> FS:  00007f0ffa346700(0000) GS:ffff88813dd00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000788000 CR3: 000000001aa9c000 CR4: 0000000000750ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> PKRU: 55555554