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authorRichard Weinberger <richard@nod.at>2016-09-16 12:45:24 +0300
committerMiklos Szeredi <mszeredi@redhat.com>2016-09-21 17:37:07 +0300
commit6a45b3628ce4dcf7498b39c87d475bab6e2a9b24 (patch)
treefb203edbc99e09b1c34be42f203704a651530ddf /fs/overlayfs/dir.c
parent8eac98b8beb4711c4ab61822cac077fd6660e820 (diff)
downloadlinux-6a45b3628ce4dcf7498b39c87d475bab6e2a9b24.tar.xz
ovl: Fix info leak in ovl_lookup_temp()
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 <richard@nod.at> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Cc: <stable@vger.kernel.org> # v3.18+ Fixes: e9be9d5e76e3 ("overlay filesystem")
Diffstat (limited to 'fs/overlayfs/dir.c')
-rw-r--r--fs/overlayfs/dir.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 1560fdc09a5f..74e696426aae 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 +38,10 @@ 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);
+ /* counter is allowed to wrap, since temp dentries are ephemeral */
+ 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) {