From: Liu Shixin Subject: fs: sysv: check sbi->s_firstdatazone in complete_read_super sbi->s_firstinodezone is initialized to 2 and sbi->s_firstdatazone is read from sbd. There's no guarantee that sbi->s_firstdatazone must bigger than sbi->s_firstinodezone. If sbi->s_firstdatazone less than 2, the filesystem can still be mounted unexpetly. At this point, sbi->s_ninodes flip to very large value and this filesystem is broken. We can observe this by executing 'df' command. When we execute, we will get an error message: "sysv_count_free_inodes: unable to read inode table" Link: https://lkml.kernel.org/r/20220330104215.530223-1-liushixin2@huawei.com Signed-off-by: Liu Shixin Reviewed-by: Christoph Hellwig Signed-off-by: Andrew Morton --- fs/sysv/super.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/fs/sysv/super.c~fs-sysv-check-sbi-s_firstdatazone-in-complete_read_super +++ a/fs/sysv/super.c @@ -312,7 +312,9 @@ static int complete_read_super(struct su sbi->s_firstinodezone = 2; flavour_setup[sbi->s_type](sbi, &sb->s_max_links); - + if (sbi->s_firstdatazone < sbi->s_firstinodezone) + return 0; + sbi->s_ndatazones = sbi->s_nzones - sbi->s_firstdatazone; sbi->s_inodes_per_block = bsize >> 6; sbi->s_inodes_per_block_1 = (bsize >> 6)-1; _