cifs: Fix integer overflow while processing acdirmax mount option

User-provided mount parameter acdirmax of type u32 is intended to have
an upper limit, but before it is validated, the value is converted from
seconds to jiffies which can lead to an integer overflow.

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

Fixes: 4c9f948142a5 ("cifs: Add new mount parameter "acdirmax" to allow caching directory metadata")
Signed-off-by: Murad Masimov <m.masimov@mt-integration.ru>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index 5f3c5967a0f5aedd00429cb3e33426d23900f49c..c983021c406bb5661fad2fbc01d3bde0558f7e2c 100644 (file)
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -1351,11 +1351,11 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
                ctx->acregmax = HZ * result.uint_32;
                break;
        case Opt_acdirmax:
-               ctx->acdirmax = HZ * result.uint_32;
-               if (ctx->acdirmax > CIFS_MAX_ACTIMEO) {
+               if (result.uint_32 > CIFS_MAX_ACTIMEO / HZ) {
                        cifs_errorf(fc, "acdirmax too large\n");
                        goto cifs_parse_mount_err;
                }
+               ctx->acdirmax = HZ * result.uint_32;
                break;
        case Opt_actimeo:
                if (HZ * result.uint_32 > CIFS_MAX_ACTIMEO) {