4.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Amir Goldstein <amir73il@xxxxxxxxx>
commit a5a927a7c82e28ea76599dee4019c41e372c911f upstream.
The optimization in ovl_cache_get_impure() that tries to remove an
unneeded "impure" xattr needs to take mnt_want_write() on upper fs.
Fixes: 4edb83bb1041 ("ovl: constant d_ino for non-merge dirs")
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/overlayfs/readdir.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -593,8 +593,15 @@ static struct ovl_dir_cache *ovl_cache_g
return ERR_PTR(res);
}
if (list_empty(&cache->entries)) {
- /* Good oportunity to get rid of an unnecessary "impure" flag */
- ovl_do_removexattr(ovl_dentry_upper(dentry), OVL_XATTR_IMPURE);
+ /*
+ * A good opportunity to get rid of an unneeded "impure" flag.
+ * Removing the "impure" xattr is best effort.
+ */
+ if (!ovl_want_write(dentry)) {
+ ovl_do_removexattr(ovl_dentry_upper(dentry),
+ OVL_XATTR_IMPURE);
+ ovl_drop_write(dentry);
+ }
ovl_clear_flag(OVL_IMPURE, d_inode(dentry));
kfree(cache);
return NULL;