From: Qu Wenruo wqu@suse.com
commit 19ea40dddf1833db868533958ca066f368862211 upstream.
[BUG] There is a bug report that injected ENOMEM error could leave a tree block locked while we return to user-space:
BTRFS info (device loop0): enabling ssd optimizations FAULT_INJECTION: forcing a failure. name failslab, interval 1, probability 0, space 0, times 0 CPU: 0 PID: 7579 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_alloc_delayed_extent_op fs/btrfs/delayed-ref.h:299 [inline] btrfs_alloc_tree_block+0x38c/0x670 fs/btrfs/extent-tree.c:4833 __btrfs_cow_block+0x16f/0x7d0 fs/btrfs/ctree.c:415 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:00007f46711b9c48 EFLAGS: 00000246 ORIG_RAX: 0000000000000055 RAX: ffffffffffffffda RBX: 000000000078c0a0 RCX: 000000000046ae99 RDX: 0000000000000000 RSI: 00000000000000a1 RDI: 0000000020005800 RBP: 00007f46711b9c80 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000017 R13: 0000000000000000 R14: 000000000078c0a0 R15: 00007ffc129da6e0
================================================ WARNING: lock held when returning to user space! 5.15.0-rc1 #16 Not tainted ------------------------------------------------ syz-executor/7579 is leaving the kernel with locks still held! 1 lock held by syz-executor/7579: #0: ffff888104b73da8 (btrfs-tree-01/1){+.+.}-{3:3}, at: __btrfs_tree_lock+0x2e/0x1a0 fs/btrfs/locking.c:112
[CAUSE] In btrfs_alloc_tree_block(), after btrfs_init_new_buffer(), the new extent buffer @buf is locked, but if later operations like adding delayed tree ref fail, we just free @buf without unlocking it, resulting above warning.
[FIX] Unlock @buf in out_free_buf: label.
Reported-by: Hao Sun sunhao.th@gmail.com Link: https://lore.kernel.org/linux-btrfs/CACkBjsZ9O6Zr0KK1yGn=1rQi6Crh1yeCRdTSBxx... CC: stable@vger.kernel.org # 5.4+ Signed-off-by: Qu Wenruo wqu@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/extent-tree.c | 1 + 1 file changed, 1 insertion(+)
--- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -4859,6 +4859,7 @@ struct extent_buffer *btrfs_alloc_tree_b out_free_delayed: btrfs_free_delayed_extent_op(extent_op); out_free_buf: + btrfs_tree_unlock(buf); free_extent_buffer(buf); out_free_reserved: btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset, 0);