linux-kernel - [PATCH] overlayfs: filter of trusted xattr results in audit.

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Message-Id: <20190829183021.87586-1-salyzyn@android.com>
Date:   Thu, 29 Aug 2019 11:30:14 -0700
From:   Mark Salyzyn <salyzyn@...roid.com>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com, Mark Salyzyn <salyzyn@...roid.com>,
        linux-kernel@...r.kernel.orga,
        linux-security-module@...r.kernel.org, stable@...r.kernel.org,
        Miklos Szeredi <miklos@...redi.hu>,
        linux-unionfs@...r.kernel.org
Subject: [PATCH] overlayfs: filter of trusted xattr results in audit.

When filtering xattr list for reading, presence of trusted xattr
results in a security audit log.  However, if there is other content
no errno will be set, and if there isn't, the errno will be -ENODATA
and not -EPERM as is usually associated with a lack of capability.
The check does not block the request to list the xattrs present.

Switch to ns_capable_noaudit to reflect a more appropriate check.

Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>
Cc: linux-kernel@...r.kernel.orga
Cc: linux-security-module@...r.kernel.org
Cc: kernel-team@...roid.com
Cc: stable@...r.kernel.org # 4.4, 4.9, 4.14 & 4.19
---
 fs/overlayfs/inode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 7663aeb85fa3..bc14781886bf 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -383,7 +383,8 @@ static bool ovl_can_list(const char *s)
 		return true;
 
 	/* Never list trusted.overlay, list other trusted for superuser only */
-	return !ovl_is_private_xattr(s) && capable(CAP_SYS_ADMIN);
+	return !ovl_is_private_xattr(s) &&
+	       ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
 }
 
 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
-- 
2.23.0.187.g17f5b7556c-goog