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Subject[PATCH -next] fs: sysv: check sbi->s_firstdatazone in complete_read_super
Date
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"

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
---
fs/sysv/super.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/sysv/super.c b/fs/sysv/super.c
index d1def0771a40..3365a30dc1e0 100644
--- a/fs/sysv/super.c
+++ b/fs/sysv/super.c
@@ -312,7 +312,9 @@ static int complete_read_super(struct super_block *sb, int silent, int size)
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;
--
2.25.1
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