cifs: Fix integer overflow while processing acregmax mount option

User-provided mount parameter acregmax 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: 5780464614f6 ("cifs: Add new parameter "acregmax" for distinct file and directory metadata timeout")
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 457452b4d42da1c529c68f77c576b0a493778331..5f3c5967a0f5aedd00429cb3e33426d23900f49c 100644 (file)
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -1344,11 +1344,11 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
                }
                break;
        case Opt_acregmax:
-               ctx->acregmax = HZ * result.uint_32;
-               if (ctx->acregmax > CIFS_MAX_ACTIMEO) {
+               if (result.uint_32 > CIFS_MAX_ACTIMEO / HZ) {
                        cifs_errorf(fc, "acregmax too large\n");
                        goto cifs_parse_mount_err;
                }
+               ctx->acregmax = HZ * result.uint_32;
                break;
        case Opt_acdirmax:
                ctx->acdirmax = HZ * result.uint_32;