[PATCH] proc: Do not invalidate dentries with submounts

[ebiederm@xmission.com (Eric W. Biederman)]

If the dcache path to a mount point is ever broken it becomes
impossible to unmount it, and we leak a vfsmount.  Therefore it is not
valid to invalidate dentries with mount points at or below them.

This patch uses the have_submounts test as the other network
filesystem revalidate routines do.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 fs/proc/base.c    |    9 +++++++++
 fs/proc/generic.c |    5 +++++
 2 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 0e71707..552d752 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1216,6 +1216,9 @@ static int pid_revalidate(struct dentry *dentry, struct nameidata *nd)
 		put_task_struct(task);
 		return 1;
 	}
+	/* Force validity if something is mounted under us */
+	if (inode && S_ISDIR(inode->i_mode) && have_submounts(dentry))
+		return 1;
 	d_drop(dentry);
 	return 0;
 }
@@ -1393,6 +1396,9 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
 		}
 		put_task_struct(task);
 	}
+	/* Force validity if something is mounted under us */
+	if (inode && S_ISDIR(inode->i_mode) && have_submounts(dentry))
+		return 1;
 	d_drop(dentry);
 	return 0;
 }
@@ -2056,6 +2062,9 @@ static int proc_base_revalidate(struct dentry *dentry, struct nameidata *nd)
 		put_task_struct(task);
 		return 1;
 	}
+	/* Force validity if something is mounted under us */
+	if (inode && S_ISDIR(inode->i_mode) && have_submounts(dentry))
+		return 1;
 	d_drop(dentry);
 	return 0;
 }
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 4abd568..233dcdc 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -370,6 +370,11 @@ static int proc_delete_dentry(struct dentry * dentry)
 
 static int proc_revalidate_dentry(struct dentry *dentry, struct nameidata *nd)
 {
+	struct inode *inode = dentry->d_inode;
+
+	/* Force validity if something is mounted under us */
+	if (inode && S_ISDIR(inode->i_mode) && have_submounts(dentry))
+		return 1;
 	d_drop(dentry);
 	return 0;
 }
-- 
1.5.3.rc6.17.g1911