- sb_csum isn't generated properly for 512- or 1024-byte filesystem block
sizes.
- Add `--no-sbcrc` option to fsck.erofs to bypass the sb_csum check.
Signed-off-by: Gao Xiang <hsiang...@linux.alibaba.com>
---
fsck/main.c | 40 ++++++++-----------------------
include/erofs/internal.h | 1 +
lib/super.c | 51 ++++++++++++++++++++++++++++++----------
man/fsck.erofs.1 | 3 +++
4 files changed, 52 insertions(+), 43 deletions(-)
diff --git a/fsck/main.c b/fsck/main.c
index cb4758b..91c193f 100644
--- a/fsck/main.c
+++ b/fsck/main.c
@@ -41,6 +41,7 @@ struct erofsfsck_cfg {
bool preserve_owner;
bool preserve_perms;
bool dump_xattrs;
+ bool nosbcrc;
};
static struct erofsfsck_cfg fsckcfg;
@@ -60,6 +61,7 @@ static struct option long_options[] = {
{"offset", required_argument, 0, 12},
{"xattrs", no_argument, 0, 13},
{"no-xattrs", no_argument, 0, 14},
+ {"no-sbcrc", no_argument, 0, 512},
{0, 0, 0, 0},
};
@@ -110,6 +112,7 @@ static void usage(int argc, char **argv)
" --extract[=X] check if all files are well encoded,
optionally\n"
" extract to X\n"
" --offset=# skip # bytes at the beginning of
IMAGE\n"
+ " --no-sbcrc bypass the superblock checksum
verification\n"
" --[no-]xattrs whether to dump extended attributes
(default off)\n"
"\n"
" -a, -A, -y no-op, for compatibility with fsck of
other filesystems\n"
@@ -244,6 +247,9 @@ static int erofsfsck_parse_options_cfg(int argc, char
**argv)
case 14:
fsckcfg.dump_xattrs = false;
break;
+ case 512:
+ fsckcfg.nosbcrc = true;
+ break;
default:
return -EINVAL;
}
@@ -322,35 +328,6 @@ static void erofsfsck_set_attributes(struct erofs_inode
*inode, char *path)
}
}
-static int erofs_check_sb_chksum(void)
-{
-#ifndef FUZZING
- u8 buf[EROFS_MAX_BLOCK_SIZE];
- u32 crc;
- struct erofs_super_block *sb;
- int ret;
-
- ret = erofs_blk_read(&g_sbi, 0, buf, 0, 1);
- if (ret) {
- erofs_err("failed to read superblock to check checksum: %d",
- ret);
- return -1;
- }
-
- sb = (struct erofs_super_block *)(buf + EROFS_SUPER_OFFSET);
- sb->checksum = 0;
-
- crc = erofs_crc32c(~0, (u8 *)sb, erofs_blksiz(&g_sbi) -
EROFS_SUPER_OFFSET);
- if (crc != g_sbi.checksum) {
- erofs_err("superblock chksum doesn't match: saved(%08xh)
calculated(%08xh)",
- g_sbi.checksum, crc);
- fsckcfg.corrupted = true;
- return -1;
- }
-#endif
- return 0;
-}
-
static int erofs_verify_xattr(struct erofs_inode *inode)
{
struct erofs_sb_info *sbi = inode->sbi;
@@ -1066,6 +1043,7 @@ int main(int argc, char *argv[])
#ifdef FUZZING
cfg.c_dbg_lvl = -1;
+ fsckcfg.nosbcrc = true;
#endif
err = erofs_dev_open(&g_sbi, cfg.c_img_path, O_RDONLY);
@@ -1080,7 +1058,9 @@ int main(int argc, char *argv[])
goto exit_dev_close;
}
- if (erofs_sb_has_sb_chksum(&g_sbi) && erofs_check_sb_chksum()) {
+ if (!fsckcfg.nosbcrc && erofs_sb_has_sb_chksum(&g_sbi) &&
+ erofs_superblock_csum_verify(&g_sbi)) {
+ fsckcfg.corrupted = true;
erofs_err("failed to verify superblock checksum");
goto exit_put_super;
}
diff --git a/include/erofs/internal.h b/include/erofs/internal.h
index bf3efb5..d380c45 100644
--- a/include/erofs/internal.h
+++ b/include/erofs/internal.h
@@ -419,6 +419,7 @@ struct erofs_buffer_head *erofs_reserve_sb(struct
erofs_bufmgr *bmgr);
int erofs_mkfs_init_devices(struct erofs_sb_info *sbi, unsigned int devices);
int erofs_write_device_table(struct erofs_sb_info *sbi);
int erofs_enable_sb_chksum(struct erofs_sb_info *sbi, u32 *crc);
+int erofs_superblock_csum_verify(struct erofs_sb_info *sbi);
/* namei.c */
int erofs_read_inode_from_disk(struct erofs_inode *vi);
diff --git a/lib/super.c b/lib/super.c
index 8efef50..5b90db5 100644
--- a/lib/super.c
+++ b/lib/super.c
@@ -259,19 +259,22 @@ int erofs_enable_sb_chksum(struct erofs_sb_info *sbi, u32
*crc)
unsigned int len;
struct erofs_super_block *sb;
- ret = erofs_blk_read(sbi, 0, buf, 0, erofs_blknr(sbi, EROFS_SUPER_END)
+ 1);
+ /*
+ * skip the first 1024 bytes, to allow for the installation
+ * of x86 boot sectors and other oddities.
+ */
+ if (erofs_blksiz(sbi) > EROFS_SUPER_OFFSET)
+ len = erofs_blksiz(sbi) - EROFS_SUPER_OFFSET;
+ else
+ len = erofs_blksiz(sbi);
+ ret = erofs_dev_read(sbi, 0, buf, EROFS_SUPER_OFFSET, len);
if (ret) {
erofs_err("failed to read superblock to set checksum: %s",
erofs_strerror(ret));
return ret;
}
- /*
- * skip the first 1024 bytes, to allow for the installation
- * of x86 boot sectors and other oddities.
- */
- sb = (struct erofs_super_block *)(buf + EROFS_SUPER_OFFSET);
-
+ sb = (struct erofs_super_block *)buf;
if (le32_to_cpu(sb->magic) != EROFS_SUPER_MAGIC_V1) {
erofs_err("internal error: not an erofs valid image");
return -EFAULT;
@@ -280,25 +283,47 @@ int erofs_enable_sb_chksum(struct erofs_sb_info *sbi, u32
*crc)
/* turn on checksum feature */
sb->feature_compat = cpu_to_le32(le32_to_cpu(sb->feature_compat) |
EROFS_FEATURE_COMPAT_SB_CHKSUM);
- if (erofs_blksiz(sbi) > EROFS_SUPER_OFFSET)
- len = erofs_blksiz(sbi) - EROFS_SUPER_OFFSET;
- else
- len = erofs_blksiz(sbi);
*crc = erofs_crc32c(~0, (u8 *)sb, len);
/* set up checksum field to erofs_super_block */
sb->checksum = cpu_to_le32(*crc);
- ret = erofs_blk_write(sbi, buf, 0, 1);
+ ret = erofs_dev_write(sbi, buf, EROFS_SUPER_OFFSET, len);
if (ret) {
erofs_err("failed to write checksummed superblock: %s",
erofs_strerror(ret));
return ret;
}
-
return 0;
}
+int erofs_superblock_csum_verify(struct erofs_sb_info *sbi)
+{
+ u32 len = erofs_blksiz(sbi), crc;
+ u8 buf[EROFS_MAX_BLOCK_SIZE];
+ struct erofs_super_block *sb;
+ int ret;
+
+ if (len > EROFS_SUPER_OFFSET)
+ len -= EROFS_SUPER_OFFSET;
+ ret = erofs_dev_read(sbi, 0, buf, EROFS_SUPER_OFFSET, len);
+ if (ret) {
+ erofs_err("failed to read superblock to calculate sbcsum: %d",
+ ret);
+ return -1;
+ }
+
+ sb = (struct erofs_super_block *)buf;
+ sb->checksum = 0;
+
+ crc = erofs_crc32c(~0, (u8 *)sb, len);
+ if (crc == sbi->checksum)
+ return 0;
+ erofs_err("invalid checksum 0x%08x, 0x%08x expected",
+ sbi->checksum, crc);
+ return -EBADMSG;
+}
+
int erofs_mkfs_init_devices(struct erofs_sb_info *sbi, unsigned int devices)
{
struct erofs_buffer_head *bh;
diff --git a/man/fsck.erofs.1 b/man/fsck.erofs.1
index af0e6ab..fb255b4 100644
--- a/man/fsck.erofs.1
+++ b/man/fsck.erofs.1
@@ -34,6 +34,9 @@ take a long time depending on the image size.
Optionally extract contents of the \fIIMAGE\fR to \fIdirectory\fR.
.TP
+.B "--no-sbcrc"
+Bypass the on-disk superblock checksum verification.
+.TP
.BI "--[no-]xattrs"
Whether to dump extended attributes during extraction (default off).
.TP
--
2.43.5
