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ext4: fix mb_cache_entry's e_refcnt leak in ext4_xattr_block_cache_find()

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Syzbot reports a warning as follows:

============================================
WARNING: CPU: 0 PID: 5075 at fs/mbcache.c:419 mb_cache_destroy+0x224/0x290
Modules linked in:
CPU: 0 PID: 5075 Comm: syz-executor199 Not tainted 6.9.0-rc6-gb947cc5bf6d7
RIP: 0010:mb_cache_destroy+0x224/0x290 fs/mbcache.c:419
Call Trace:
 <TASK>
 ext4_put_super+0x6d4/0xcd0 fs/ext4/super.c:1375
 generic_shutdown_super+0x136/0x2d0 fs/super.c:641
 kill_block_super+0x44/0x90 fs/super.c:1675
 ext4_kill_sb+0x68/0xa0 fs/ext4/super.c:7327
[...]
============================================

This is because when finding an entry in ext4_xattr_block_cache_find(), if
ext4_sb_bread() returns -ENOMEM, the ce's e_refcnt, which has already grown
in the __entry_find(), won't be put away, and eventually trigger the above
issue in mb_cache_destroy() due to reference count leakage.

So call mb_cache_entry_put() on the -ENOMEM error branch as a quick fix.

Reported-by: syzbot+dd43bd0f7474512edc47@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=dd43bd0f7474512edc47
Fixes: fb265c9cb4 ("ext4: add ext4_sb_bread() to disambiguate ENOMEM cases")
Cc: stable@kernel.org
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240504075526.2254349-2-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Baokun Li 2024-05-04 15:55:25 +08:00 committed by Theodore Ts'o
parent 8b57de1c5e
commit 0c0b4a49d3
1 changed files with 3 additions and 1 deletions
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4
fs/ext4/xattr.c
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@ -3117,8 +3117,10 @@ ext4_xattr_block_cache_find(struct inode *inode,
bh = ext4_sb_bread(inode->i_sb, ce->e_value, REQ_PRIO);
if (IS_ERR(bh)) {
if (PTR_ERR(bh) == -ENOMEM)
if (PTR_ERR(bh) == -ENOMEM) {
mb_cache_entry_put(ea_block_cache, ce);
return NULL;
}
bh = NULL;
EXT4_ERROR_INODE(inode, "block %lu read error",
(unsigned long)ce->e_value);