[PATCH] drivers/staging/exfat - by default, prohibit mount of fat/vfat

[Valdis Klētnieks]

Concerns have been raised about the exfat driver accidentally mounting
fat/vfat file systems.  Add an extra configure option to help prevent that.

Suggested-by: Christoph Hellwig <h...@infradead.org>
Signed-off-by: Valdis Kletnieks <valdis.kletni...@vt.edu>

diff --git a/drivers/staging/exfat/Kconfig b/drivers/staging/exfat/Kconfig
index 78b32aa2ca19..1df177b1dc72 100644
--- a/drivers/staging/exfat/Kconfig
+++ b/drivers/staging/exfat/Kconfig
@@ -4,6 +4,14 @@ config EXFAT_FS
        help
          This adds support for the exFAT file system.
 
+config EXFAT_DONT_MOUNT_VFAT
+       bool "Prohibit mounting of fat/vfat filesysems by exFAT"
+       default y
+       help
+         By default, the exFAT driver will only mount exFAT filesystems, and 
refuse
+         to mount fat/vfat filesystems.  Set this to 'n' to allow the exFAT 
driver
+         to mount these filesystems.
+
 config EXFAT_DISCARD
        bool "enable discard support"
        depends on EXFAT_FS
diff --git a/drivers/staging/exfat/exfat_super.c 
b/drivers/staging/exfat/exfat_super.c
index 5b5c2ca8c9aa..7fdb5b8bc928 100644
--- a/drivers/staging/exfat/exfat_super.c
+++ b/drivers/staging/exfat/exfat_super.c
@@ -486,10 +486,16 @@ static int ffsMountVol(struct super_block *sb)
                        break;
 
        if (i < 53) {
+#ifdef CONFIG_EXFAT_DONT_MOUNT_VFAT
+               ret = -EINVAL;
+               printk(KERN_INFO "EXFAT: Attempted to mount VFAT filesystem\n");
+               goto out;
+#else
                if (GET16(p_pbr->bpb + 11)) /* num_fat_sectors */
                        ret = fat16_mount(sb, p_pbr);
                else
                        ret = fat32_mount(sb, p_pbr);
+#endif
        } else {
                ret = exfat_mount(sb, p_pbr);
        }