From: Pratik Shinde <[email protected]> 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/[email protected] Signed-off-by: Pratik Shinde <[email protected]> Reviewed-by: Chao Yu <[email protected]> Cc: Dan Carpenter <[email protected]> Signed-off-by: Gao Xiang <[email protected]> --- changes since v6: - fix kunmap(data) to kunmap(page) by mistake reported by Dan Carpenter; fs/erofs/Kconfig | 1 + fs/erofs/erofs_fs.h | 3 ++- fs/erofs/internal.h | 1 + fs/erofs/super.c | 36 ++++++++++++++++++++++++++++++++++-- 4 files changed, 38 insertions(+), 3 deletions(-) diff --git a/fs/erofs/Kconfig b/fs/erofs/Kconfig index 9d634d3a1845..74b0aaa7114c 100644 --- a/fs/erofs/Kconfig +++ b/fs/erofs/Kconfig @@ -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 diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h index b1ee5654750d..385fa49c7749 100644 --- a/fs/erofs/erofs_fs.h +++ b/fs/erofs/erofs_fs.h @@ -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]; }; diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h index 544a453f3076..96d97eab88e3 100644 --- a/fs/erofs/internal.h +++ b/fs/erofs/internal.h @@ -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; diff --git a/fs/erofs/super.c b/fs/erofs/super.c index 0e369494f2f2..849c0bdf49d9 100644 --- a/fs/erofs/super.c +++ b/fs/erofs/super.c @@ -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; } -- 2.17.1
