From 0a295bf1d1aab79a115af903278f749dd64fe55d 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: Ben Hutchings --- 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 cd50df554584..c608d805f509 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3301,10 +3301,15 @@ 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;