linux-kernel - [PATCH v16 4/4] overlayfs: inode_owner_or

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Message-Id: <20201019115239.2732422-5-salyzyn@android.com>
Date:   Mon, 19 Oct 2020 04:52:39 -0700
From:   Mark Salyzyn <salyzyn@...roid.com>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com, John Stultz <john.stultz@...aro.org>,
        Mark Salyzyn <salyzyn@...gle.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        linux-security-module@...r.kernel.org
Subject: [PATCH v16 4/4] overlayfs: inode_owner_or_capable called during execv

From: John Stultz <john.stultz@...aro.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@...aro.org>
Signed-off-by: Mark Salyzyn <salyzyn@...gle.com>
Fixes: 05acefb4872da ("ovl: check permission to open real file")
To: linux-fsdevel@...r.kernel.org
To: linux-unionfs@...r.kernel.org
Cc: Stephen Smalley <sds@...ho.nsa.gov>
Cc: linux-kernel@...r.kernel.org
Cc: linux-security-module@...r.kernel.org
Cc: kernel-team@...roid.com

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