[PATCH 4/4] ext4: add sanity checking to count_overhead()
From: Theodore Ts'o <tytso@mit.edu>
Date: 2016-11-18 18:38:49
Subsystem:
ext4 file system, filesystems (vfs and infrastructure), the rest · Maintainers:
"Theodore Ts'o", Alexander Viro, Christian Brauner, Linus Torvalds
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 <tytso@mit.edu> --- 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 689c02df1af4..2d8a49d74f56 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c@@ -3195,10 +3195,15 @@ 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;
--
2.11.0.rc0.7.gbe5a750