The function uses the memory address of a struct dentry as unique id.
While the address-based directory entry is only visible to root
it is IMHO still worth fixing since the temporary name does not have
to be a kernel address. It can be any unique number. Replace it by an
atomic integer which is allowed to wrap around.

Signed-off-by: Richard Weinberger <>
 fs/overlayfs/dir.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 1560fdc..6e00a08 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -14,6 +14,7 @@
 #include <linux/cred.h>
 #include <linux/posix_acl.h>
 #include <linux/posix_acl_xattr.h>
+#include <linux/atomic.h>
 #include "overlayfs.h"
 void ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
@@ -37,8 +38,9 @@ struct dentry *ovl_lookup_temp(struct dentry *workdir, struct 
dentry *dentry)
        struct dentry *temp;
        char name[20];
+       static atomic_t temp_id = ATOMIC_INIT(0);
-       snprintf(name, sizeof(name), "#%lx", (unsigned long) dentry);
+       snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
        temp = lookup_one_len(name, workdir, strlen(name));
        if (!IS_ERR(temp) && temp->d_inode) {

Reply via email to