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ext4: add missing down_write_data_sem in mext_move_extent().

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Commit 962e8a01ea ("ext4: introduce mext_move_extent()") attempts to
call ext4_swap_extents() on the failure path to recover the swapped
extents, but fails to acquire locks for the two inode->i_data_sem,
triggering the BUG_ON statement in ext4_swap_extents().

This issue can be fixed by calling ext4_double_down_write_data_sem()
before ext4_swap_extents().

Signed-off-by: Julian Sun <sunjunchao@bytedance.com>
Reported-by: syzbot+4ea6bd8737669b423aae@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69368649.a70a0220.38f243.0093.GAE@google.com/
Fixes: 962e8a01ea ("ext4: introduce mext_move_extent()")
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Link: https://patch.msgid.link/20251208123713.1971068-1-sunjunchao@bytedance.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Julian Sun
2025-12-08 20:37:13 +08:00
committed by Theodore Ts'o
parent cd16edba1c
commit 0ef7ef4227
1 changed files with 2 additions and 0 deletions
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2
fs/ext4/move_extent.c
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@@ -393,9 +393,11 @@ out:
repair_branches:
ret2 = 0;
ext4_double_down_write_data_sem(orig_inode, donor_inode);
r_len = ext4_swap_extents(handle, donor_inode, orig_inode,
mext->donor_lblk, orig_map->m_lblk,
*m_len, 0, &ret2);
ext4_double_up_write_data_sem(orig_inode, donor_inode);
if (ret2 || r_len != *m_len) {
ext4_error_inode_block(orig_inode, (sector_t)(orig_map->m_lblk),
EIO, "Unable to copy data block, data will be lost!");