cifs: fix integer overflow in match_server()

[ Upstream commit 2510859475d7f46ed7940db0853f3342bf1b65ee ]

The echo_interval is not limited in any way during mounting,
which makes it possible to write a large number to it. This can
cause an overflow when multiplying ctx->echo_interval by HZ in
match_server().

Add constraints for echo_interval to smb3_fs_context_parse_param().

Found by Linux Verification Center (linuxtesting.org) with Svace.

Fixes: adfeb3e00e8e1 ("cifs: Make echo interval tunable")
Cc: stable@vger.kernel.org
Signed-off-by: Roman Smirnov <r.smirnov@omp.ru>
Signed-off-by: Steve French <stfrench@microsoft.com>
[ Adapted to older CIFS filesystem structure and mount option parsing ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 2c0522d97e037d9b9dd557d20ea2f9ceb13cdacb..5fc418f9210a5c6fda765a8b4372cf18cb6512b8 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1915,6 +1915,11 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
                                         __func__);
                                goto cifs_parse_mount_err;
                        }
+                       if (option < SMB_ECHO_INTERVAL_MIN ||
+                           option > SMB_ECHO_INTERVAL_MAX) {
+                               cifs_dbg(VFS, "echo interval is out of bounds\n");
+                               goto cifs_parse_mount_err;
+                       }
                        vol->echo_interval = option;
                        break;
                case Opt_snapshot: