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From: Miklos Szeredi <miklos@szeredi.hu>
To: akpm@linux-foundation.org, hch@infradead.org, serue@us.ibm.com
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [patch 02/10] unprivileged mounts: allow unprivileged umount
Date: Tue, 05 Feb 2008 22:36:18 +0100	[thread overview]
Message-ID: <20080205213657.480430286@szeredi.hu> (raw)
In-Reply-To: <20080205213616.343721693@szeredi.hu>

[-- Attachment #1: unprivileged-mounts-allow-unprivileged-umount.patch --]
[-- Type: text/plain, Size: 1523 bytes --]

From: Miklos Szeredi <mszeredi@suse.cz>

The owner doesn't need sysadmin capabilities to call umount().

Similar behavior as umount(8) on mounts having "user=UID" option in /etc/mtab.
The difference is that umount also checks /etc/fstab, presumably to exclude
another mount on the same mountpoint.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: Serge Hallyn <serue@us.ibm.com>
---

Index: linux/fs/namespace.c
===================================================================
--- linux.orig/fs/namespace.c	2008-02-04 23:47:50.000000000 +0100
+++ linux/fs/namespace.c	2008-02-04 23:47:53.000000000 +0100
@@ -1033,6 +1033,27 @@ static int do_umount(struct vfsmount *mn
 	return retval;
 }
 
+static bool is_mount_owner(struct vfsmount *mnt, uid_t uid)
+{
+	return (mnt->mnt_flags & MNT_USER) && mnt->mnt_uid == uid;
+}
+
+/*
+ * umount is permitted for
+ *  - sysadmin
+ *  - mount owner, if not forced umount
+ */
+static bool permit_umount(struct vfsmount *mnt, int flags)
+{
+	if (capable(CAP_SYS_ADMIN))
+		return true;
+
+	if (flags & MNT_FORCE)
+		return false;
+
+	return is_mount_owner(mnt, current->fsuid);
+}
+
 /*
  * Now umount can handle mount points as well as block devices.
  * This is important for filesystems which use unnamed block devices.
@@ -1056,7 +1077,7 @@ asmlinkage long sys_umount(char __user *
 		goto dput_and_out;
 
 	retval = -EPERM;
-	if (!capable(CAP_SYS_ADMIN))
+	if (!permit_umount(nd.path.mnt, flags))
 		goto dput_and_out;
 
 	retval = do_umount(nd.path.mnt, flags);

--

  parent reply	other threads:[~2008-02-05 21:38 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-05 21:36 [patch 00/10] mount ownership and unprivileged mount syscall (v8) Miklos Szeredi
2008-02-05 21:36 ` [patch 01/10] unprivileged mounts: add user mounts to the kernel Miklos Szeredi
2008-02-05 21:36 ` Miklos Szeredi [this message]
2008-02-05 21:36 ` [patch 03/10] unprivileged mounts: propagate error values from clone_mnt Miklos Szeredi
2008-02-05 21:36 ` [patch 04/10] unprivileged mounts: account user mounts Miklos Szeredi
2008-02-05 21:36 ` [patch 05/10] unprivileged mounts: allow unprivileged bind mounts Miklos Szeredi
2008-02-05 21:36 ` [patch 06/10] unprivileged mounts: allow unprivileged mounts Miklos Szeredi
2008-02-05 21:36 ` [patch 07/10] unprivileged mounts: add sysctl tunable for "safe" property Miklos Szeredi
2008-02-06 20:21   ` Serge E. Hallyn
2008-02-06 21:11     ` Miklos Szeredi
2008-02-06 22:45       ` Serge E. Hallyn
2008-02-07  8:09         ` Miklos Szeredi
2008-02-07 14:05           ` Serge E. Hallyn
2008-02-07 14:36             ` Miklos Szeredi
2008-02-07 16:57               ` Serge E. Hallyn
2008-02-07 15:33   ` Aneesh Kumar K.V
2008-02-07 16:24     ` Miklos Szeredi
2008-02-05 21:36 ` [patch 08/10] unprivileged mounts: make fuse safe Miklos Szeredi
2008-02-05 21:36 ` [patch 09/10] unprivileged mounts: propagation: inherit owner from parent Miklos Szeredi
2008-02-05 21:36 ` [patch 10/10] unprivileged mounts: add "no submounts" flag Miklos Szeredi
2008-02-15  6:21 ` [patch 00/10] mount ownership and unprivileged mount syscall (v8) Andrew Morton
2008-02-15  9:01   ` Christoph Hellwig
2008-02-15  9:09     ` Andrew Morton
2008-02-15  9:14       ` Christoph Hellwig
2008-02-18 11:47         ` Miklos Szeredi
2008-02-23 16:09           ` Al Viro
2008-02-23 17:33             ` Miklos Szeredi
2008-02-23 18:57               ` Al Viro
2008-02-23 19:48                 ` Miklos Szeredi
  -- strict thread matches above, loose matches on Subject: below --
2008-01-16 12:31 [patch 00/10] mount ownership and unprivileged mount syscall (v7) Miklos Szeredi
2008-01-16 12:31 ` [patch 02/10] unprivileged mounts: allow unprivileged umount Miklos Szeredi
2007-04-27 12:04 [patch 00/10] mount ownership and unprivileged mount syscall (v5) Miklos Szeredi
2007-04-27 12:04 ` [patch 02/10] unprivileged mounts: allow unprivileged umount Miklos Szeredi

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