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| author | André Almeida <andrealmeid@igalia.com> | 2025-04-29 15:38:50 -0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-06-27 11:11:24 +0100 |
| commit | ec5f0b44125c0c7d8f472b34ac7a61a6cf12e246 (patch) | |
| tree | 9a3b6fc4aca9b52ecdab80dcb6249bec05d4e175 | |
| parent | 6dbda47fe8bd6aa978c150bc9d321a286d2cc3f4 (diff) | |
ovl: Fix nested backing file paths
commit 924577e4f6ca473de1528953a0e13505fae61d7b upstream.
When the lowerdir of an overlayfs is a merged directory of another
overlayfs, ovl_open_realfile() will fail to open the real file and point
to a lower dentry copy, without the proper parent path. After this,
d_path() will then display the path incorrectly as if the file is placed
in the root directory.
This bug can be triggered with the following setup:
mkdir -p ovl-A/lower ovl-A/upper ovl-A/merge ovl-A/work
mkdir -p ovl-B/upper ovl-B/merge ovl-B/work
cp /bin/cat ovl-A/lower/
mount -t overlay overlay -o \
lowerdir=ovl-A/lower,upperdir=ovl-A/upper,workdir=ovl-A/work \
ovl-A/merge
mount -t overlay overlay -o \
lowerdir=ovl-A/merge,upperdir=ovl-B/upper,workdir=ovl-B/work \
ovl-B/merge
ovl-A/merge/cat /proc/self/maps | grep --color cat
ovl-B/merge/cat /proc/self/maps | grep --color cat
The first cat will correctly show `/ovl-A/merge/cat`, while the second
one shows just `/cat`.
To fix that, uses file_user_path() inside of backing_file_open() to get
the correct file path for the dentry.
Co-developed-by: John Schoenick <johns@valvesoftware.com>
Signed-off-by: John Schoenick <johns@valvesoftware.com>
Signed-off-by: André Almeida <andrealmeid@igalia.com>
Fixes: def3ae83da02 ("fs: store real path instead of fake path in backing file f_path")
Cc: <stable@vger.kernel.org> # v6.7
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | fs/overlayfs/file.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index 4444c78e2e0c..94095058da34 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -48,8 +48,8 @@ static struct file *ovl_open_realfile(const struct file *file, if (!inode_owner_or_capable(real_idmap, realinode)) flags &= ~O_NOATIME; - realfile = backing_file_open(&file->f_path, flags, realpath, - current_cred()); + realfile = backing_file_open(file_user_path((struct file *) file), + flags, realpath, current_cred()); } revert_creds(old_cred); |