[PATCH 3.18 110/120] ext4: always check block group bounds in ext4_init_block_bitmap()

Greg Kroah-Hartman
2018-10-11T15:41:24Z

From: Theodore Ts'o <tytso@mit.edu>

commit 819b23f1c501b17b9694325471789e6b5cc2d0d2 upstream.

Regardless of whether the flex_bg feature is set, we should always
check to make sure the bits we are setting in the block bitmap are
within the block group bounds.

https://bugzilla.kernel.org/show_bug.cgi?id=199865

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ext4/balloc.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -184,7 +184,6 @@ static int ext4_init_block_bitmap(struct
unsigned int bit, bit_max;
struct ext4_sb_info *sbi = EXT4_SB(sb);
ext4_fsblk_t start, tmp;
- int flex_bg = 0;
struct ext4_group_info *grp;

J_ASSERT_BH(bh, buffer_locked(bh));
@@ -217,22 +216,19 @@ static int ext4_init_block_bitmap(struct

start = ext4_group_first_block_no(sb, block_group);

- if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
- flex_bg = 1;
-
/* Set bits for block and inode bitmaps, and inode table */
tmp = ext4_block_bitmap(sb, gdp);
- if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
+ if (ext4_block_in_group(sb, tmp, block_group))
ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);

tmp = ext4_inode_bitmap(sb, gdp);
- if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
+ if (ext4_block_in_group(sb, tmp, block_group))
ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);

tmp = ext4_inode_table(sb, gdp);
for (; tmp < ext4_inode_table(sb, gdp) +
sbi->s_itb_per_group; tmp++) {
- if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
+ if (ext4_block_in_group(sb, tmp, block_group))
ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
}