[RESEND PATCH v18 4/4] overlayfs: inode_owner_or_capable called during execv

[Mark Salyzyn]

From: John Stultz <john.stultz at linaro.org>

Using old_creds as an indication that we are not overriding the
credentials, bypass call to inode_owner_or_capable.  This solves
a problem with all execv calls being blocked when using the caller's
credentials.

Signed-off-by: John Stultz <john.stultz at linaro.org>
Signed-off-by: Mark Salyzyn <salyzyn at android.com>
Fixes: 05acefb4872da ("ovl: check permission to open real file")
C: linux-fsdevel at vger.kernel.org
C: linux-unionfs at vger.kernel.org
Cc: Stephen Smalley <sds at tycho.nsa.gov>
Cc: linux-kernel at vger.kernel.org
Cc: linux-security-module at vger.kernel.org
Cc: kernel-team at android.com
Cc: selinux at vger.kernel.org

v18 - rebase

v17 - rebase

v16 - introduced fix over rebased series
---
 fs/overlayfs/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index b1357bb067d9..9ab9663b02d8 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -53,7 +53,7 @@ static struct file *ovl_open_realfile(const struct file *file,
 	err = inode_permission(realinode, MAY_OPEN | acc_mode);
 	if (err) {
 		realfile = ERR_PTR(err);
-	} else if (!inode_owner_or_capable(realinode)) {
+	} else if (old_cred && !inode_owner_or_capable(realinode)) {
 		realfile = ERR_PTR(-EPERM);
 	} else {
 		realfile = open_with_fake_path(&file->f_path, flags, realinode,
-- 
2.29.0.rc1.297.gfa9743e501-goog