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")
Cc: <stable@xxxxxxxxxxxxxxx> #v4.14
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/readdir.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 8c98578d27a1..001c79297bc5 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -593,8 +593,15 @@ static struct ovl_dir_cache *ovl_cache_get_impure(struct path *path)
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;
--
2.7.4
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