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authorEric W. Biederman <ebiederm@xmission.com>2014-10-04 14:44:03 -0700
committerEric W. Biederman <ebiederm@xmission.com>2014-12-02 10:46:48 -0600
commitb2f5d4dc38e034eecb7987e513255265ff9aa1cf (patch)
tree7a2205fdc3392feb549dfc55ce2c9f567b730936
parent4a44a19b470a886997d6647a77bb3e38dcbfa8c5 (diff)
umount: Disallow unprivileged mount force
Forced unmount affects not just the mount namespace but the underlying superblock as well. Restrict forced unmount to the global root user for now. Otherwise it becomes possible a user in a less privileged mount namespace to force the shutdown of a superblock of a filesystem in a more privileged mount namespace, allowing a DOS attack on root. Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
-rw-r--r--fs/namespace.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 3a1a87dc33df..43b16af8af30 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1544,6 +1544,9 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
goto dput_and_out;
if (mnt->mnt.mnt_flags & MNT_LOCKED)
goto dput_and_out;
+ retval = -EPERM;
+ if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
+ goto dput_and_out;
retval = do_umount(mnt, flags);
dput_and_out: