From 6f94ab6656ceffb3f2a972c8de4c554502b6f2b7 Mon Sep 17 00:00:00 2001
From: Tom Rini <trini@konsulko.com>
Date: Fri, 22 Jul 2016 17:59:11 -0400
Subject: [PATCH] ext4: Refuse to mount filesystems with 64bit feature set
With e2fsprogs after 1.43 the 64bit and metadata_csum features are
enabled by default. The metadata_csum feature changes how
ext4_group_desc->bg_checksum is calculated, which would break write
support. The 64bit feature however introduces changes such that it
cannot be read by implementations that do not support it. Since we do
not support this, we must not mount it.
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: Stefan Roese <sr@denx.de>
Reported-by: Andrew Bradford <andrew.bradford@kodakalaris.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
---
fs/ext4/ext4_common.c | 10 ++++++++++
include/ext4fs.h | 1 +
2 files changed, 11 insertions(+)
diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index 40b798a43f..eb49fce04c 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -2229,6 +2229,16 @@ int ext4fs_mount(unsigned part_length)
if (__le16_to_cpu(data->sblock.magic) != EXT2_MAGIC)
goto fail;
+ /*
+ * The 64bit feature was enabled when metadata_csum was enabled
+ * and we do not support metadata_csum (and cannot reliably find
+ * files when it is set. Refuse to mount.
+ */
+ if (data->sblock.feature_incompat & EXT4_FEATURE_INCOMPAT_64BIT) {
+ printf("Unsupported feature found (64bit, possibly metadata_csum), not mounting\n");
+ goto fail;
+ }
+
if (__le32_to_cpu(data->sblock.revision_level == 0))
fs->inodesz = 128;
else
diff --git a/include/ext4fs.h b/include/ext4fs.h
index cc765ae468..13d2c5603b 100644
--- a/include/ext4fs.h
+++ b/include/ext4fs.h
@@ -32,6 +32,7 @@
#define EXT4_EXT_MAGIC 0xf30a
#define EXT4_FEATURE_RO_COMPAT_GDT_CSUM 0x0010
#define EXT4_FEATURE_INCOMPAT_EXTENTS 0x0040
+#define EXT4_FEATURE_INCOMPAT_64BIT 0x0080
#define EXT4_INDIRECT_BLOCKS 12
#define EXT4_BG_INODE_UNINIT 0x0001
--
2.39.5