On Fri, Nov 08, 2019 at 04:11:56PM +0000, fdmanana@xxxxxxxxxx wrote:
> From: Filipe Manana <fdmanana@xxxxxxxx>
>
> During rename exchange we might have successfully log the new name in the
> source root's log tree, in which case we leave our log context (allocated
> on stack) in the root's list of log contextes. However we might fail to
> log the new name in the destination root, in which case we fallback to
> a transaction commit later and never sync the log of the source root,
> which causes the source root log context to remain in the list of log
> contextes. This later causes invalid memory accesses because the context
> was allocated on stack and after rename exchange finishes the stack gets
> reused and overwritten for other purposes.
>
> The kernel's linked list corruption detector (CONFIG_DEBUG_LIST=y) can
> detect this and report something like the following:
>
> [ 691.489929] ------------[ cut here ]------------
> [ 691.489947] list_add corruption. prev->next should be next (ffff88819c944530), but was ffff8881c23f7be4. (prev=ffff8881c23f7a38).
> [ 691.489967] WARNING: CPU: 2 PID: 28933 at lib/list_debug.c:28 __list_add_valid+0x95/0xe0
> (...)
> [ 691.489998] CPU: 2 PID: 28933 Comm: fsstress Not tainted 5.4.0-rc6-btrfs-next-62 #1
> [ 691.490001] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
> [ 691.490003] RIP: 0010:__list_add_valid+0x95/0xe0
> (...)
> [ 691.490007] RSP: 0018:ffff8881f0b3faf8 EFLAGS: 00010282
> [ 691.490010] RAX: 0000000000000000 RBX: ffff88819c944530 RCX: 0000000000000000
> [ 691.490011] RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffffffffa2c497e0
> [ 691.490013] RBP: ffff8881f0b3fe68 R08: ffffed103eaa4115 R09: ffffed103eaa4114
> [ 691.490015] R10: ffff88819c944000 R11: ffffed103eaa4115 R12: 7fffffffffffffff
> [ 691.490016] R13: ffff8881b4035610 R14: ffff8881e7b84728 R15: 1ffff1103e167f7b
> [ 691.490019] FS: 00007f4b25ea2e80(0000) GS:ffff8881f5500000(0000) knlGS:0000000000000000
> [ 691.490021] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 691.490022] CR2: 00007fffbb2d4eec CR3: 00000001f2a4a004 CR4: 00000000003606e0
> [ 691.490025] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 691.490027] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [ 691.490029] Call Trace:
> [ 691.490058] btrfs_log_inode_parent+0x667/0x2730 [btrfs]
> [ 691.490083] ? join_transaction+0x24a/0xce0 [btrfs]
> [ 691.490107] ? btrfs_end_log_trans+0x80/0x80 [btrfs]
> [ 691.490111] ? dget_parent+0xb8/0x460
> [ 691.490116] ? lock_downgrade+0x6b0/0x6b0
> [ 691.490121] ? rwlock_bug.part.0+0x90/0x90
> [ 691.490127] ? do_raw_spin_unlock+0x142/0x220
> [ 691.490151] btrfs_log_dentry_safe+0x65/0x90 [btrfs]
> [ 691.490172] btrfs_sync_file+0x9f1/0xc00 [btrfs]
> [ 691.490195] ? btrfs_file_write_iter+0x1800/0x1800 [btrfs]
> [ 691.490198] ? rcu_read_lock_any_held.part.11+0x20/0x20
> [ 691.490204] ? __do_sys_newstat+0x88/0xd0
> [ 691.490207] ? cp_new_stat+0x5d0/0x5d0
> [ 691.490218] ? do_fsync+0x38/0x60
> [ 691.490220] do_fsync+0x38/0x60
> [ 691.490224] __x64_sys_fdatasync+0x32/0x40
> [ 691.490228] do_syscall_64+0x9f/0x540
> [ 691.490233] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [ 691.490235] RIP: 0033:0x7f4b253ad5f0
> (...)
> [ 691.490239] RSP: 002b:00007fffbb2d6078 EFLAGS: 00000246 ORIG_RAX: 000000000000004b
> [ 691.490242] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f4b253ad5f0
> [ 691.490244] RDX: 00007fffbb2d5fe0 RSI: 00007fffbb2d5fe0 RDI: 0000000000000003
> [ 691.490245] RBP: 000000000000000d R08: 0000000000000001 R09: 00007fffbb2d608c
> [ 691.490247] R10: 00000000000002e8 R11: 0000000000000246 R12: 00000000000001f4
> [ 691.490248] R13: 0000000051eb851f R14: 00007fffbb2d6120 R15: 00005635a498bda0
>
> This started happening recently when running some test cases from fstests
> like btrfs/004 for example, because support for rename exchange was added
> last week to fsstress from fstests.
>
> So fix this by deleting the log context for the source root from the list
> if we have logged the new name in the source root.
>
> Reported-by: Su Yue <Damenly_Su@xxxxxxx>
> Fixes: d4682ba03ef618 ("Btrfs: sync log after logging new name")
> CC: stable@xxxxxxxxxxxxxxx # 4.19+
> Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Thanks, added to misc-next, most likely to be sent in a late 5.4-rc pull
request too.
