34 lines
1.1 KiB
Diff
34 lines
1.1 KiB
Diff
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From: "Eric W. Biederman" <ebiederm@xmission.com>
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Date: Sat, 4 Oct 2014 14:44:03 -0700
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Subject: [PATCH] umount: Disallow unprivileged mount force
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Forced unmount affects not just the mount namespace but the underlying
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superblock as well. Restrict forced unmount to the global root user
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for now. Otherwise it becomes possible a user in a less privileged
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mount namespace to force the shutdown of a superblock of a filesystem
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in a more privileged mount namespace, allowing a DOS attack on root.
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Cc: stable@vger.kernel.org
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Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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---
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fs/namespace.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/fs/namespace.c b/fs/namespace.c
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index 3a1a87dc33df..43b16af8af30 100644
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--- a/fs/namespace.c
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+++ b/fs/namespace.c
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@@ -1544,6 +1544,9 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
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goto dput_and_out;
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if (mnt->mnt.mnt_flags & MNT_LOCKED)
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goto dput_and_out;
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+ retval = -EPERM;
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+ if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
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+ goto dput_and_out;
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retval = do_umount(mnt, flags);
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dput_and_out:
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--
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2.1.0
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