Just verify the remaining unknown on-disk data instead of allocating a
temporary buffer for the whole superblock and zeroing out the checksum
field since .magic(EROFS_SUPER_MAGIC_V1) is verified and .checksum(0)
is fixed.
Signed-off-by: Gao Xiang <hsiang...@linux.alibaba.com>
---
fs/erofs/erofs_fs.h | 3 ++-
fs/erofs/super.c | 30 +++++++++++-------------------
2 files changed, 13 insertions(+), 20 deletions(-)
diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
index c8f2ae845bd2..199395ed1c1f 100644
--- a/fs/erofs/erofs_fs.h
+++ b/fs/erofs/erofs_fs.h
@@ -9,6 +9,7 @@
#ifndef __EROFS_FS_H
#define __EROFS_FS_H
+/* to allow for x86 boot sectors and other oddities. */
#define EROFS_SUPER_OFFSET 1024
#define EROFS_FEATURE_COMPAT_SB_CHKSUM 0x00000001
@@ -54,7 +55,7 @@ struct erofs_deviceslot {
/* erofs on-disk super block (currently 128 bytes) */
struct erofs_super_block {
__le32 magic; /* file system magic number */
- __le32 checksum; /* crc32c(super_block) */
+ __le32 checksum; /* crc32c to avoid unexpected on-disk overlap */
__le32 feature_compat;
__u8 blkszbits; /* filesystem block size in bit shift */
__u8 sb_extslots; /* superblock size = 128 + sb_extslots * 16 */
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 9166054370aa..faf1506c47f5 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -39,29 +39,21 @@ void _erofs_printk(struct super_block *sb, const char *fmt,
...)
static int erofs_superblock_csum_verify(struct super_block *sb, void *sbdata)
{
- size_t len = 1 << EROFS_SB(sb)->blkszbits;
- struct erofs_super_block *dsb;
- u32 expected_crc, crc;
+ struct erofs_super_block *dsb = sbdata + EROFS_SUPER_OFFSET;
+ u32 len = 1 << EROFS_SB(sb)->blkszbits, crc;
if (len > EROFS_SUPER_OFFSET)
len -= EROFS_SUPER_OFFSET;
+ len -= offsetof(struct erofs_super_block, checksum) +
+ sizeof(dsb->checksum);
- dsb = kmemdup(sbdata + EROFS_SUPER_OFFSET, len, GFP_KERNEL);
- if (!dsb)
- return -ENOMEM;
-
- expected_crc = le32_to_cpu(dsb->checksum);
- dsb->checksum = 0;
- /* to allow for x86 boot sectors and other oddities. */
- crc = crc32c(~0, dsb, len);
- kfree(dsb);
-
- if (crc != expected_crc) {
- erofs_err(sb, "invalid checksum 0x%08x, 0x%08x expected",
- crc, expected_crc);
- return -EBADMSG;
- }
- return 0;
+ /* skip .magic(pre-verified) and .checksum(0) fields */
+ crc = crc32c(0x5045B54A, (&dsb->checksum) + 1, len);
+ if (crc == le32_to_cpu(dsb->checksum))
+ return 0;
+ erofs_err(sb, "invalid checksum 0x%08x, 0x%08x expected",
+ crc, le32_to_cpu(dsb->checksum));
+ return -EBADMSG;
}
static void erofs_inode_init_once(void *ptr)
--
2.43.5
