6.12-stable review patch. If anyone has any objections, please let me know.
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From: Yongjian Sun sunyongjian1@huawei.com
[ Upstream commit f70681e9e6066ab7b102e6b46a336a8ed67812ae ]
There is an issue in the kernel:
In tmpfs, when using the "ls" command to list the contents of a directory with a large number of files, glibc performs the getdents call in multiple rounds. If a concurrent unlink occurs between these getdents calls, it may lead to duplicate directory entries in the ls output. One possible reproduction scenario is as follows:
Create 1026 files and execute ls and rm concurrently:
for i in {1..1026}; do echo "This is file $i" > /tmp/dir/file$i done
ls /tmp/dir rm /tmp/dir/file4 ->getdents(file1026-file5) ->unlink(file4)
->getdents(file5,file3,file2,file1)
It is expected that the second getdents call to return file3 through file1, but instead it returns an extra file5.
The root cause of this problem is in the offset_dir_lookup function. It uses mas_find to determine the starting position for the current getdents call. Since mas_find locates the first position that is greater than or equal to mas->index, when file4 is deleted, it ends up returning file5.
It can be fixed by replacing mas_find with mas_find_rev, which finds the first position that is less than or equal to mas->index.
Fixes: b9b588f22a0c ("libfs: Use d_children list to iterate simple_offset directories") Signed-off-by: Yongjian Sun sunyongjian1@huawei.com Link: https://lore.kernel.org/r/20250320034417.555810-1-sunyongjian@huaweicloud.co... Reviewed-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/libfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/libfs.c b/fs/libfs.c index b0f262223b535..3cb49463a8496 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -492,7 +492,7 @@ offset_dir_lookup(struct dentry *parent, loff_t offset) found = find_positive_dentry(parent, NULL, false); else { rcu_read_lock(); - child = mas_find(&mas, DIR_OFFSET_MAX); + child = mas_find_rev(&mas, DIR_OFFSET_MIN); found = find_positive_dentry(parent, child, false); rcu_read_unlock(); }