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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Jeffrey Mitchell <jeffrey.mitchell@starlab.io>,
        Tyler Hicks <code@tyhicks.com>
Subject: [PATCH 5.11 020/342] ecryptfs: fix kernel panic with null dev_name
Date:   Mon, 10 May 2021 12:16:50 +0200
Message-Id: <20210510102010.777714351@linuxfoundation.org>
In-Reply-To: <20210510102010.096403571@linuxfoundation.org>
References: <20210510102010.096403571@linuxfoundation.org>
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From: Jeffrey Mitchell <jeffrey.mitchell@starlab.io>

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@vger.kernel.org
Signed-off-by: Jeffrey Mitchell <jeffrey.mitchell@starlab.io>
Signed-off-by: Tyler Hicks <code@tyhicks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/ecryptfs/main.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -492,6 +492,12 @@ 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";