From: Filipe Manana fdmanana@suse.com
commit e6c617102c7e4ac1398cb0b98ff1f0727755b520 upstream.
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@gmx.com Fixes: d4682ba03ef618 ("Btrfs: sync log after logging new name") CC: stable@vger.kernel.org # 4.19+ Tested-by: Su Yue Damenly_Su@gmx.com Signed-off-by: Filipe Manana fdmanana@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/inode.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
--- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -9700,6 +9700,18 @@ out_fail: commit_transaction = true; } if (commit_transaction) { + /* + * We may have set commit_transaction when logging the new name + * in the destination root, in which case we left the source + * root context in the list of log contextes. So make sure we + * remove it to avoid invalid memory accesses, since the context + * was allocated in our stack frame. + */ + if (sync_log_root) { + mutex_lock(&root->log_mutex); + list_del_init(&ctx_root.list); + mutex_unlock(&root->log_mutex); + } ret = btrfs_commit_transaction(trans); } else { int ret2; @@ -9713,6 +9725,9 @@ out_notrans: if (old_ino == BTRFS_FIRST_FREE_OBJECTID) up_read(&fs_info->subvol_sem);
+ ASSERT(list_empty(&ctx_root.list)); + ASSERT(list_empty(&ctx_dest.list)); + return ret; }