[PATCH 4.9 011/240] ecryptfs: fix kernel panic with null dev_name

[Greg Kroah-Hartman]

From: Jeffrey Mitchell <jeffrey.mitchell@xxxxxxxxxx>

commit 9046625511ad8dfbc8c6c2de16b3532c43d68d48 upstream.

When mounting eCryptfs, a null "dev_name" argument to ecryptfs_mount()
causes a kernel panic if the parsed options are valid. The easiest way to
reproduce this is to call mount() from userspace with an existing
eCryptfs mount's options and a "source" argument of 0.

Error out if "dev_name" is null in ecryptfs_mount()

Fixes: 237fead61998 ("[PATCH] ecryptfs: fs/Makefile and fs/Kconfig")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jeffrey Mitchell <jeffrey.mitchell@xxxxxxxxxx>
Signed-off-by: Tyler Hicks <code@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/ecryptfs/main.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -506,6 +506,12 @@ static struct dentry *ecryptfs_mount(str
 		goto out;
 	}
 
+	if (!dev_name) {
+		rc = -EINVAL;
+		err = "Device name cannot be null";
+		goto out;
+	}
+
 	rc = ecryptfs_parse_options(sbi, raw_data, &check_ruid);
 	if (rc) {
 		err = "Error parsing options";