6.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: Amir Goldstein amir73il@gmail.com
[ Upstream commit ad1423922781e6552f18d055a5742b1cff018cdc ]
e8bd877fb76bb9f3 ("ovl: fix possible double unlink") added a sanity check of !d_unhashed(child) to try to verify that child dentry was not unlinked while parent dir was unlocked.
This "was not unlink" check has a false positive result in the case of casefolded parent dir, because in that case, ovl_create_temp() returns an unhashed dentry after ovl_create_real() gets an unhashed dentry from ovl_lookup_upper() and makes it positive.
To avoid returning unhashed dentry from ovl_create_temp(), let ovl_create_real() lookup again after making the newdentry positive, so it always returns a hashed positive dentry (or an error).
This fixes the error in ovl_parent_lock() in ovl_check_rename_whiteout() after ovl_create_temp() and allows mount of overlayfs with casefolding enabled layers.
Reported-by: André Almeida andrealmeid@igalia.com Closes: https://lore.kernel.org/r/18704e8c-c734-43f3-bc7c-b8be345e1bf5@igalia.com/ Suggested-by: Neil Brown neil@brown.name Reviewed-by: Neil Brown neil@brown.name Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/overlayfs/dir.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index dbd63a74df4b1..039e829aa7dee 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -205,12 +205,32 @@ struct dentry *ovl_create_real(struct ovl_fs *ofs, struct dentry *parent, err = -EPERM; } } - if (!err && WARN_ON(!newdentry->d_inode)) { + if (err) + goto out; + + if (WARN_ON(!newdentry->d_inode)) { /* * Not quite sure if non-instantiated dentry is legal or not. * VFS doesn't seem to care so check and warn here. */ err = -EIO; + } else if (d_unhashed(newdentry)) { + struct dentry *d; + /* + * Some filesystems (i.e. casefolded) may return an unhashed + * negative dentry from the ovl_lookup_upper() call before + * ovl_create_real(). + * In that case, lookup again after making the newdentry + * positive, so ovl_create_upper() always returns a hashed + * positive dentry. + */ + d = ovl_lookup_upper(ofs, newdentry->d_name.name, parent, + newdentry->d_name.len); + dput(newdentry); + if (IS_ERR_OR_NULL(d)) + err = d ? PTR_ERR(d) : -ENOENT; + else + return d; } out: if (err) {