From 2b47f7351dd6e24e54acbd6883fccc6c5650374e Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Fri, 18 Nov 2016 13:37:47 -0500 Subject: [PATCH] ext4: add sanity checking to count_overhead() commit c48ae41bafe31e9a66d8be2ced4e42a6b57fa814 upstream. The commit "ext4: sanity check the block and cluster size at mount time" should prevent any problems, but in case the superblock is modified while the file system is mounted, add an extra safety check to make sure we won't overrun the allocated buffer. Signed-off-by: Theodore Ts'o Signed-off-by: Jiri Slaby --- fs/ext4/super.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 6c67a988bfcee..6362896f58756 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3257,10 +3257,15 @@ static int count_overhead(struct super_block *sb, ext4_group_t grp, ext4_set_bit(s++, buf); count++; } - for (j = ext4_bg_num_gdb(sb, grp); j > 0; j--) { - ext4_set_bit(EXT4_B2C(sbi, s++), buf); - count++; + j = ext4_bg_num_gdb(sb, grp); + if (s + j > EXT4_BLOCKS_PER_GROUP(sb)) { + ext4_error(sb, "Invalid number of block group " + "descriptor blocks: %d", j); + j = EXT4_BLOCKS_PER_GROUP(sb) - s; } + count += j; + for (; j > 0; j--) + ext4_set_bit(EXT4_B2C(sbi, s++), buf); } if (!count) return 0; -- 2.47.2