There are some backward incompatible optimizations pending for months, mainly due to on-disk format expensions.
However, we should ensure that it cannot be mounted with old kernels. Otherwise, it will causes unexpected behaviors.
Fixes: ba2b77a82022 ("staging: erofs: add super block operations") Cc: stable@vger.kernel.org # 4.19+ Signed-off-by: Gao Xiang gaoxiang25@huawei.com --- drivers/staging/erofs/erofs_fs.h | 11 +++++++++-- drivers/staging/erofs/super.c | 8 ++++++++ 2 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/erofs/erofs_fs.h b/drivers/staging/erofs/erofs_fs.h index fa52898df006..531821757845 100644 --- a/drivers/staging/erofs/erofs_fs.h +++ b/drivers/staging/erofs/erofs_fs.h @@ -17,10 +17,16 @@ #define EROFS_SUPER_MAGIC_V1 0xE0F5E1E2 #define EROFS_SUPER_OFFSET 1024
+/* + * Any bits that aren't in EROFS_ALL_REQUIREMENTS should be + * incompatible with this kernel version. + */ +#define EROFS_ALL_REQUIREMENTS 0 + struct erofs_super_block { /* 0 */__le32 magic; /* in the little endian */ /* 4 */__le32 checksum; /* crc32c(super_block) */ -/* 8 */__le32 features; +/* 8 */__le32 features; /* extra features for the image */ /* 12 */__u8 blkszbits; /* support block_size == PAGE_SIZE only */ /* 13 */__u8 reserved;
@@ -34,8 +40,9 @@ struct erofs_super_block { /* 44 */__le32 xattr_blkaddr; /* 48 */__u8 uuid[16]; /* 128-bit uuid for volume */ /* 64 */__u8 volume_name[16]; /* volume name */ +/* 80 */__le32 requirements; /* all mandatory minimum requirements */
-/* 80 */__u8 reserved2[48]; /* 128 bytes */ +/* 84 */__u8 reserved2[44]; /* 128 bytes */ } __packed;
/* diff --git a/drivers/staging/erofs/super.c b/drivers/staging/erofs/super.c index f580d4ef77a1..815e5825db59 100644 --- a/drivers/staging/erofs/super.c +++ b/drivers/staging/erofs/super.c @@ -104,6 +104,14 @@ static int superblock_read(struct super_block *sb) goto out; }
+ /* check if the kernel meets all mandatory requirements */ + if (le32_to_cpu(layout->requirements) & (~EROFS_ALL_REQUIREMENTS)) { + errln("too old to meet minimum requirements: %x supported: %x", + le32_to_cpu(layout->requirements), + EROFS_ALL_REQUIREMENTS); + goto out; + } + sbi->blocks = le32_to_cpu(layout->blocks); sbi->meta_blkaddr = le32_to_cpu(layout->meta_blkaddr); #ifdef CONFIG_EROFS_FS_XATTR