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erofs: support superblock checksum

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Introduce superblock checksum feature in order to
check at mounting time.

Note that the first 1024 bytes are ignore for x86
boot sectors and other oddities.

Link: https://lore.kernel.org/r/20191104024937.113939-1-gaoxiang25@huawei.com
Signed-off-by: Pratik Shinde <pratikshinde320@gmail.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
This commit is contained in:
Pratik Shinde 2019-11-04 10:49:37 +08:00 committed by Gao Xiang
parent a93f8c3687
commit b858a4844c
4 changed files with 38 additions and 3 deletions
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1
fs/erofs/Kconfig
View File

@ -3,6 +3,7 @@
config EROFS_FS
tristate "EROFS filesystem support"
depends on BLOCK
select LIBCRC32C
help
EROFS (Enhanced Read-Only File System) is a lightweight
read-only file system with modern designs (eg. page-sized

3
fs/erofs/erofs_fs.h
View File

@ -11,6 +11,8 @@
#define EROFS_SUPER_OFFSET 1024
#define EROFS_FEATURE_COMPAT_SB_CHKSUM 0x00000001
/*
* Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
* be incompatible with this kernel version.
@ -37,7 +39,6 @@ struct erofs_super_block {
__u8 uuid[16]; /* 128-bit uuid for volume */
__u8 volume_name[16]; /* volume name */
__le32 feature_incompat;
__u8 reserved2[44];
};

1
fs/erofs/internal.h
View File

@ -85,6 +85,7 @@ struct erofs_sb_info {
u8 uuid[16]; /* 128-bit uuid for volume */
u8 volume_name[16]; /* volume name */
u32 feature_compat;
u32 feature_incompat;
unsigned int mount_opt;

36
fs/erofs/super.c
View File

@ -9,6 +9,7 @@
#include <linux/statfs.h>
#include <linux/parser.h>
#include <linux/seq_file.h>
#include <linux/crc32c.h>
#include "xattr.h"
#define CREATE_TRACE_POINTS
@ -46,6 +47,30 @@ 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)
{
struct erofs_super_block *dsb;
u32 expected_crc, crc;
dsb = kmemdup(sbdata + EROFS_SUPER_OFFSET,
EROFS_BLKSIZ - EROFS_SUPER_OFFSET, 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, EROFS_BLKSIZ - EROFS_SUPER_OFFSET);
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;
@ -112,7 +137,7 @@ static int erofs_read_superblock(struct super_block *sb)
sbi = EROFS_SB(sb);
data = kmap_atomic(page);
data = kmap(page);
dsb = (struct erofs_super_block *)(data + EROFS_SUPER_OFFSET);
ret = -EINVAL;
@ -121,6 +146,13 @@ static int erofs_read_superblock(struct super_block *sb)
goto out;
}
sbi->feature_compat = le32_to_cpu(dsb->feature_compat);
if (sbi->feature_compat & EROFS_FEATURE_COMPAT_SB_CHKSUM) {
ret = erofs_superblock_csum_verify(sb, data);
if (ret)
goto out;
}
blkszbits = dsb->blkszbits;
/* 9(512 bytes) + LOG_SECTORS_PER_BLOCK == LOG_BLOCK_SIZE */
if (blkszbits != LOG_BLOCK_SIZE) {
@ -155,7 +187,7 @@ static int erofs_read_superblock(struct super_block *sb)
}
ret = 0;
out:
kunmap_atomic(data);
kunmap(page);
put_page(page);
return ret;
}