lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Mon, 15 Sep 2014 12:26:39 -0700
From:	Greg Kroah-Hartman <>
Cc:	Greg Kroah-Hartman <>,,
	"Serge E. Hallyn" <>,
	"Eric W. Biederman" <>
Subject: [PATCH 3.10 41/71] mnt: Move the test for MNT_LOCK_READONLY from change_mount_flags into do_remount

3.10-stable review patch.  If anyone has any objections, please let me know.


From: "Eric W. Biederman" <>

commit 07b645589dcda8b7a5249e096fece2a67556f0f4 upstream.

There are no races as locked mount flags are guaranteed to never change.

Moving the test into do_remount makes it more visible, and ensures all
filesystem remounts pass the MNT_LOCK_READONLY permission check.  This
second case is not an issue today as filesystem remounts are guarded
by capable(CAP_DAC_ADMIN) and thus will always fail in less privileged
mount namespaces, but it could become an issue in the future.

Acked-by: Serge E. Hallyn <>
Signed-off-by: "Eric W. Biederman" <>
Signed-off-by: Greg Kroah-Hartman <>

 fs/namespace.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1764,9 +1764,6 @@ static int change_mount_flags(struct vfs
 	if (readonly_request == __mnt_is_readonly(mnt))
 		return 0;
-	if (mnt->mnt_flags & MNT_LOCK_READONLY)
-		return -EPERM;
 	if (readonly_request)
 		error = mnt_make_readonly(real_mount(mnt));
@@ -1792,6 +1789,16 @@ static int do_remount(struct path *path,
 	if (path->dentry != path->mnt->mnt_root)
 		return -EINVAL;
+	/* Don't allow changing of locked mnt flags.
+	 *
+	 * No locks need to be held here while testing the various
+	 * MNT_LOCK flags because those flags can never be cleared
+	 * once they are set.
+	 */
+	if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) &&
+	    !(mnt_flags & MNT_READONLY)) {
+		return -EPERM;
+	}
 	err = security_sb_remount(sb, data);
 	if (err)
 		return err;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists