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vfs: Ignore unlocked mounts in fs_fully_visible

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Limit the mounts fs_fully_visible considers to locked mounts.
Unlocked can always be unmounted so considering them adds hassle
but no security benefit.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2015-01-07 08:10:09 -06:00
parent 8c6cf9cc82
commit ceeb0e5d39
1 changed files with 6 additions and 2 deletions
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8
fs/namespace.c
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@ -3205,11 +3205,15 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
continue;
/* This mount is not fully visible if there are any child mounts
* that cover anything except for empty directories.
/* This mount is not fully visible if there are any
* locked child mounts that cover anything except for
* empty directories.
*/
list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
struct inode *inode = child->mnt_mountpoint->d_inode;
/* Only worry about locked mounts */
if (!(mnt->mnt.mnt_flags & MNT_LOCKED))
continue;
if (!S_ISDIR(inode->i_mode))
goto next;
if (inode->i_nlink > 2)