On Thu, Aug 06, 2020 at 03:32:21PM +0100, Al Viro wrote:
> On Thu, Aug 06, 2020 at 04:17:32PM +0200, Christoph Hellwig wrote:
> > Fix for umount03 below. The other one works fine here, but from
> > your logs this might be a follow on if you run it after umount without
> > the fix.
>
> Ugh...
>
> How about
> static int may_umount(const struct path *path, int flags)
may_umount is already take. But with can_umount this would work:
---
>From e4ccb3da160831a43eeea48c68d2d43fd7cf6724 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@xxxxxx>
Date: Thu, 6 Aug 2020 16:07:10 +0200
Subject: fs: fix a struct path leak in path_umount
Make sure we also put the dentry and vfsmnt in the illegal flags
and !may_umount cases.
Fixes: 41525f56e256 ("fs: refactor ksys_umount")
Reported-by: Vikas Kumar <vikas.kumar2@xxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/namespace.c | 32 ++++++++++++++++++--------------
1 file changed, 18 insertions(+), 14 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index a7301790abb211..1c74a46367df4e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1706,34 +1706,38 @@ static inline bool may_mandlock(void)
}
#endif
-int path_umount(struct path *path, int flags)
+static int can_umount(const struct path *path, int flags)
{
- struct mount *mnt;
- int retval;
+ struct mount *mnt = real_mount(path->mnt);
if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
return -EINVAL;
if (!may_mount())
return -EPERM;
-
- mnt = real_mount(path->mnt);
- retval = -EINVAL;
if (path->dentry != path->mnt->mnt_root)
- goto dput_and_out;
+ return -EINVAL;
if (!check_mnt(mnt))
- goto dput_and_out;
+ return -EINVAL;
if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
- goto dput_and_out;
- retval = -EPERM;
+ return -EINVAL;
if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
- goto dput_and_out;
+ return -EPERM;
+ return 0;
+}
+
+int path_umount(struct path *path, int flags)
+{
+ struct mount *mnt = real_mount(path->mnt);
+ int ret;
+
+ ret = can_umount(path, flags);
+ if (!ret)
+ ret = do_umount(mnt, flags);
- retval = do_umount(mnt, flags);
-dput_and_out:
/* we mustn't call path_put() as that would clear mnt_expiry_mark */
dput(path->dentry);
mntput_no_expire(mnt);
- return retval;
+ return ret;
}
static int ksys_umount(char __user *name, int flags)
--
2.27.0
