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/[email protected]
Signed-off-by: Liu Shixin <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions