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author | Yongjian Sun <sunyongjian1@huawei.com> | 2025-03-20 11:44:17 +0800 |
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committer | Christian Brauner <brauner@kernel.org> | 2025-03-20 14:28:18 +0100 |
commit | f70681e9e6066ab7b102e6b46a336a8ed67812ae (patch) | |
tree | 7db3bb105d979087e18e02996dddb59ffc0d6eed /rust/helpers/helpers.c | |
parent | d55011469b41d9da6c06cb1c4a4da7a87fe155bc (diff) | |
download | lwn-f70681e9e6066ab7b102e6b46a336a8ed67812ae.tar.gz lwn-f70681e9e6066ab7b102e6b46a336a8ed67812ae.zip |
libfs: Fix duplicate directory entry in offset_dir_lookup
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.com
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'rust/helpers/helpers.c')
0 files changed, 0 insertions, 0 deletions