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From: Theodore Ts'o <tytso@mit.edu>
Date: Wed, 13 Jun 2018 23:00:48 -0400
Subject: ext4: always check block group bounds in ext4_init_block_bitmap()
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit?id=dcf37fefac3f699aa1341f86bcd7808ccc651c33
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-10878
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 4.17: adjust context]
---
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_feature_flex_bg(sb))
- 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);
}
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