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btrfs: fix extent map leak in NOCOW direct I/O write

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btrfs_dio_iomap_begin() calls btrfs_get_extent(), which returns an
extent map reference that must be dropped on all exit paths.

For direct writes into a NOCOW range, btrfs_get_blocks_direct_write()
keeps using that extent map and asks btrfs_create_dio_extent() to
allocate the ordered extent. If that fails, for example because
btrfs_alloc_ordered_extent() fails, the function returns the error
without dropping the input extent map. The PREALLOC path avoided this by
dropping the input extent map before replacing it with the newly created
one.

Check the error from btrfs_create_dio_extent() before replacing the
map and drop the input extent map on failure.

Fixes: 5f9a8a51d8 ("Btrfs: add semaphore to synchronize direct IO writes with fsync")
CC: stable@vger.kernel.org
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Shuangpeng Bai 2026-07-05 01:46:35 -04:00 committed by David Sterba
parent ee2851074b
commit 3f950867c3
1 changed files with 13 additions and 6 deletions
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19
fs/btrfs/direct-io.c
View File

@ -280,17 +280,24 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map,
em2 = btrfs_create_dio_extent(BTRFS_I(inode), dio_data, start,
&file_extent, type);
btrfs_dec_nocow_writers(bg);
if (type == BTRFS_ORDERED_PREALLOC) {
if (IS_ERR(em2)) {
ret = PTR_ERR(em2);
btrfs_free_extent_map(em);
*map = NULL;
goto out;
}
/*
* True NOCOW writes don't need to create a new extent map,
* while PREALLOC writes must replace the existing one.
*/
if (em2) {
ASSERT(type == BTRFS_ORDERED_PREALLOC);
btrfs_free_extent_map(em);
*map = em2;
em = em2;
}
if (IS_ERR(em2)) {
ret = PTR_ERR(em2);
goto out;
}
dio_data->nocow_done = true;
} else {
/* Our caller expects us to free the input extent map. */