[PATCH] erofs: deprecate superblock checksum feature

From: Jingbo Xu
Date: Thu Jul 13 2023 - 23:38:44 EST


Later we're going to introduce fs-verity based verification for the
whole image. Make the superblock checksum feature deprecated.

Signed-off-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
---
fs/erofs/Kconfig | 1 -
fs/erofs/super.c | 44 +++++---------------------------------------
2 files changed, 5 insertions(+), 40 deletions(-)

diff --git a/fs/erofs/Kconfig b/fs/erofs/Kconfig
index f259d92c9720..ebcb1f6a426a 100644
--- a/fs/erofs/Kconfig
+++ b/fs/erofs/Kconfig
@@ -4,7 +4,6 @@ config EROFS_FS
tristate "EROFS filesystem support"
depends on BLOCK
select FS_IOMAP
- select LIBCRC32C
help
EROFS (Enhanced Read-Only File System) is a lightweight read-only
file system with modern designs (e.g. no buffer heads, inline
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 9d6a3c6158bd..bb6a966ac4d4 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -8,7 +8,6 @@
#include <linux/statfs.h>
#include <linux/parser.h>
#include <linux/seq_file.h>
-#include <linux/crc32c.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include <linux/dax.h>
@@ -51,33 +50,6 @@ void _erofs_info(struct super_block *sb, const char *function,
va_end(args);
}

-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;
-
- if (len > EROFS_SUPER_OFFSET)
- len -= EROFS_SUPER_OFFSET;
-
- 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;
-}
-
static void erofs_inode_init_once(void *ptr)
{
struct erofs_inode *vi = ptr;
@@ -113,15 +85,16 @@ static void erofs_free_inode(struct inode *inode)
static bool check_layout_compatibility(struct super_block *sb,
struct erofs_super_block *dsb)
{
- const unsigned int feature = le32_to_cpu(dsb->feature_incompat);
+ struct erofs_sb_info *sbi = EROFS_SB(sb);

- EROFS_SB(sb)->feature_incompat = feature;
+ sbi->feature_compat = le32_to_cpu(dsb->feature_compat);
+ sbi->feature_incompat = le32_to_cpu(dsb->feature_incompat);

/* check if current kernel meets all mandatory requirements */
- if (feature & (~EROFS_ALL_FEATURE_INCOMPAT)) {
+ if (sbi->feature_incompat & (~EROFS_ALL_FEATURE_INCOMPAT)) {
erofs_err(sb,
"unidentified incompatible feature %x, please upgrade kernel version",
- feature & ~EROFS_ALL_FEATURE_INCOMPAT);
+ sbi->feature_incompat & ~EROFS_ALL_FEATURE_INCOMPAT);
return false;
}
return true;
@@ -365,13 +338,6 @@ static int erofs_read_superblock(struct super_block *sb)
goto out;
}

- sbi->feature_compat = le32_to_cpu(dsb->feature_compat);
- if (erofs_sb_has_sb_chksum(sbi)) {
- ret = erofs_superblock_csum_verify(sb, data);
- if (ret)
- goto out;
- }
-
ret = -EINVAL;
if (!check_layout_compatibility(sb, dsb))
goto out;
--
2.19.1.6.gb485710b