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Subject[PATCH v4 3/3] btrfs: qgroup: fix sleep from invalid context bug in update_qgroup_limit_item()
Date
Syzkaller reported BUG as follows:

BUG: sleeping function called from invalid context at
include/linux/sched/mm.h:274
Call Trace:
<TASK>
dump_stack_lvl+0xcd/0x134
__might_resched.cold+0x222/0x26b
kmem_cache_alloc+0x2e7/0x3c0
update_qgroup_limit_item+0xe1/0x390
btrfs_qgroup_inherit+0x147b/0x1ee0
create_subvol+0x4eb/0x1710
btrfs_mksubvol+0xfe5/0x13f0
__btrfs_ioctl_snap_create+0x2b0/0x430
btrfs_ioctl_snap_create_v2+0x25a/0x520
btrfs_ioctl+0x2a1c/0x5ce0
__x64_sys_ioctl+0x193/0x200
do_syscall_64+0x35/0x80

Fix this by delaying the limit item updates until unlock the spin lock.

Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
---
fs/btrfs/qgroup.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index ca609a70d067..f84507ca3b99 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2867,6 +2867,8 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
bool need_rescan = false;
u32 level_size = 0;
u64 nums;
+ bool update_limit = false;
+ int err;

/*
* There are only two callers of this function.
@@ -2957,10 +2959,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
dstgroup->max_excl = inherit->lim.max_excl;
dstgroup->rsv_rfer = inherit->lim.rsv_rfer;
dstgroup->rsv_excl = inherit->lim.rsv_excl;
-
- ret = btrfs_update_quoto_limit(trans, dstgroup, fs_info);
- if (ret)
- goto unlock;
+ update_limit = true;
}

if (srcid) {
@@ -2987,6 +2986,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
dstgroup->max_excl = srcgroup->max_excl;
dstgroup->rsv_rfer = srcgroup->rsv_rfer;
dstgroup->rsv_excl = srcgroup->rsv_excl;
+ update_limit = false;

qgroup_dirty(fs_info, dstgroup);
qgroup_dirty(fs_info, srcgroup);
@@ -3055,6 +3055,11 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,

unlock:
spin_unlock(&fs_info->qgroup_lock);
+ if (update_limit) {
+ err = btrfs_update_quoto_limit(trans, dstgroup, fs_info);
+ if (err)
+ ret = err;
+ }
if (!ret)
ret = btrfs_sysfs_add_one_qgroup(fs_info, dstgroup);
out:
--
2.31.1
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