From: Yongjian Sun <sunyongjian1@xxxxxxxxxx>
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@xxxxxxxxxx>
---
fs/libfs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/libfs.c b/fs/libfs.c
index 8444f5cc4064..dc042a975a56 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -496,7 +496,7 @@ 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();
}
--
2.39.2
