cifs: Fix integer overflow while processing acdirmax mount option

[ Upstream commit 5b29891f91dfb8758baf1e2217bef4b16b2b165b ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
index d86cbed997fdd61e108bad051ad9b3c82667033c..9b1c0e0dfc63b6b91e25eb85d991bcd61675538a 100644 (file)
--- a/fs/cifs/fs_context.c
+++ b/fs/cifs/fs_context.c
@@ -1062,11 +1062,11 @@ 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) {