ext4: fix bitmap position validation
Un-revert "ext4: add validity checks for bitmap block numbers" and apply this new fix on top of it.
This commit is contained in:
Ben Hutchings
parent
c3c6a03a9c
commit
5b54699034
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@ -18,12 +18,11 @@ linux (4.16.4-1) UNRELEASED; urgency=medium
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* [x86,arm64] Disable code signing for upload to unstable
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* debian/lib/python/debian_linux/debian.py: Fix binNMU changelog parsing
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* debian/lib/python/debian_linux/debian.py: Fix binNMU revision parsing
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* Revert "ext4: add validity checks for bitmap block numbers", which
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caused a regression
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* xfs: enhance dinode verifier (CVE-2018-10322)
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* xfs: set format back to extents if xfs_bmap_extents_to_btree
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(CVE-2018-10323)
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* udeb: Add algif_skcipher to crypto-modules (Closes: #896968)
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* ext4: fix bitmap position validation (fixes regression in 4.15.17-1)
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[ Vagrant Cascadian ]
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* [arm64] Add patches to support SATA on Tegra210/Jetson-TX1.
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96
debian/patches/bugfix/all/ext4-add-validity-checks-for-bitmap-block-numbers.patch
vendored
Normal file
96
debian/patches/bugfix/all/ext4-add-validity-checks-for-bitmap-block-numbers.patch
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@ -0,0 +1,96 @@
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From: Theodore Ts'o <tytso@mit.edu>
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Date: Mon, 26 Mar 2018 23:54:10 -0400
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Subject: ext4: add validity checks for bitmap block numbers
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Origin: https://git.kernel.org/linus/7dac4a1726a9c64a517d595c40e95e2d0d135f6f
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Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-1093
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An privileged attacker can cause a crash by mounting a crafted ext4
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image which triggers a out-of-bounds read in the function
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ext4_valid_block_bitmap() in fs/ext4/balloc.c.
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This issue has been assigned CVE-2018-1093.
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BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=199181
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BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1560782
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Reported-by: Wen Xu <wen.xu@gatech.edu>
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Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Cc: stable@vger.kernel.org
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---
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fs/ext4/balloc.c | 16 ++++++++++++++--
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fs/ext4/ialloc.c | 7 +++++++
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2 files changed, 21 insertions(+), 2 deletions(-)
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--- a/fs/ext4/balloc.c
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+++ b/fs/ext4/balloc.c
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@@ -338,20 +338,25 @@ static ext4_fsblk_t ext4_valid_block_bit
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/* check whether block bitmap block number is set */
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blk = ext4_block_bitmap(sb, desc);
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offset = blk - group_first_block;
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- if (!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
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+ if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
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+ !ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
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/* bad block bitmap */
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return blk;
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/* check whether the inode bitmap block number is set */
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blk = ext4_inode_bitmap(sb, desc);
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offset = blk - group_first_block;
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- if (!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
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+ if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
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+ !ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
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/* bad block bitmap */
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return blk;
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/* check whether the inode table block number is set */
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blk = ext4_inode_table(sb, desc);
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offset = blk - group_first_block;
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+ if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
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+ EXT4_B2C(sbi, offset + sbi->s_itb_per_group) >= sb->s_blocksize)
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+ return blk;
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next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
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EXT4_B2C(sbi, offset + sbi->s_itb_per_group),
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EXT4_B2C(sbi, offset));
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@@ -417,6 +422,7 @@ struct buffer_head *
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ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
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{
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struct ext4_group_desc *desc;
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+ struct ext4_sb_info *sbi = EXT4_SB(sb);
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struct buffer_head *bh;
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ext4_fsblk_t bitmap_blk;
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int err;
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@@ -425,6 +431,12 @@ ext4_read_block_bitmap_nowait(struct sup
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if (!desc)
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return ERR_PTR(-EFSCORRUPTED);
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bitmap_blk = ext4_block_bitmap(sb, desc);
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+ if ((bitmap_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
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+ (bitmap_blk >= ext4_blocks_count(sbi->s_es))) {
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+ ext4_error(sb, "Invalid block bitmap block %llu in "
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+ "block_group %u", bitmap_blk, block_group);
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+ return ERR_PTR(-EFSCORRUPTED);
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+ }
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bh = sb_getblk(sb, bitmap_blk);
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if (unlikely(!bh)) {
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ext4_error(sb, "Cannot get buffer for block bitmap - "
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--- a/fs/ext4/ialloc.c
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+++ b/fs/ext4/ialloc.c
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@@ -122,6 +122,7 @@ static struct buffer_head *
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ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
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{
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struct ext4_group_desc *desc;
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+ struct ext4_sb_info *sbi = EXT4_SB(sb);
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struct buffer_head *bh = NULL;
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ext4_fsblk_t bitmap_blk;
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int err;
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@@ -131,6 +132,12 @@ ext4_read_inode_bitmap(struct super_bloc
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return ERR_PTR(-EFSCORRUPTED);
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bitmap_blk = ext4_inode_bitmap(sb, desc);
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+ if ((bitmap_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
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+ (bitmap_blk >= ext4_blocks_count(sbi->s_es))) {
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+ ext4_error(sb, "Invalid inode bitmap blk %llu in "
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+ "block_group %u", bitmap_blk, block_group);
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+ return ERR_PTR(-EFSCORRUPTED);
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+ }
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bh = sb_getblk(sb, bitmap_blk);
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if (unlikely(!bh)) {
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ext4_error(sb, "Cannot read inode bitmap - "
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@ -0,0 +1,76 @@
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From: Lukas Czerner <lczerner@redhat.com>
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Date: Tue, 24 Apr 2018 11:31:44 -0400
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Subject: ext4: fix bitmap position validation
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Origin: https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit?id=22be37acce25d66ecf6403fc8f44df9c5ded2372
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Currently in ext4_valid_block_bitmap() we expect the bitmap to be
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positioned anywhere between 0 and s_blocksize clusters, but that's
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wrong because the bitmap can be placed anywhere in the block group. This
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causes false positives when validating bitmaps on perfectly valid file
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system layouts. Fix it by checking whether the bitmap is within the group
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boundary.
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The problem can be reproduced using the following
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mkfs -t ext3 -E stride=256 /dev/vdb1
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mount /dev/vdb1 /mnt/test
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cd /mnt/test
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wget https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.16.3.tar.xz
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tar xf linux-4.16.3.tar.xz
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This will result in the warnings in the logs
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EXT4-fs error (device vdb1): ext4_validate_block_bitmap:399: comm tar: bg 84: block 2774529: invalid block bitmap
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[ Changed slightly for clarity and to not drop a overflow test -- TYT ]
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Signed-off-by: Lukas Czerner <lczerner@redhat.com>
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Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Reported-by: Ilya Dryomov <idryomov@gmail.com>
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Fixes: 7dac4a1726a9 ("ext4: add validity checks for bitmap block numbers")
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Cc: stable@vger.kernel.org
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---
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fs/ext4/balloc.c | 9 +++++----
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1 file changed, 5 insertions(+), 4 deletions(-)
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diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
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index a33d8fb1bf2a..508b905d744d 100644
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--- a/fs/ext4/balloc.c
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+++ b/fs/ext4/balloc.c
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@@ -321,6 +321,7 @@ static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb,
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struct ext4_sb_info *sbi = EXT4_SB(sb);
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ext4_grpblk_t offset;
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ext4_grpblk_t next_zero_bit;
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+ ext4_grpblk_t max_bit = EXT4_CLUSTERS_PER_GROUP(sb);
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ext4_fsblk_t blk;
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ext4_fsblk_t group_first_block;
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@@ -338,7 +339,7 @@ static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb,
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/* check whether block bitmap block number is set */
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blk = ext4_block_bitmap(sb, desc);
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offset = blk - group_first_block;
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- if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
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+ if (offset < 0 || EXT4_B2C(sbi, offset) >= max_bit ||
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!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
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/* bad block bitmap */
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return blk;
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@@ -346,7 +347,7 @@ static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb,
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/* check whether the inode bitmap block number is set */
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blk = ext4_inode_bitmap(sb, desc);
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offset = blk - group_first_block;
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- if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
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+ if (offset < 0 || EXT4_B2C(sbi, offset) >= max_bit ||
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!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
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/* bad block bitmap */
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return blk;
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@@ -354,8 +355,8 @@ static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb,
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/* check whether the inode table block number is set */
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blk = ext4_inode_table(sb, desc);
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offset = blk - group_first_block;
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- if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
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- EXT4_B2C(sbi, offset + sbi->s_itb_per_group) >= sb->s_blocksize)
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+ if (offset < 0 || EXT4_B2C(sbi, offset) >= max_bit ||
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+ EXT4_B2C(sbi, offset + sbi->s_itb_per_group) >= max_bit)
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return blk;
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next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
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EXT4_B2C(sbi, offset + sbi->s_itb_per_group),
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@ -141,6 +141,8 @@ features/all/lockdown/arm64-add-kernel-config-option-to-lock-down-when.patch
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debian/i386-686-pae-pci-set-pci-nobios-by-default.patch
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bugfix/all/xfs-enhance-dinode-verifier.patch
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bugfix/all/xfs-set-format-back-to-extents-if-xfs_bmap_extents_t.patch
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bugfix/all/ext4-add-validity-checks-for-bitmap-block-numbers.patch
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bugfix/all/ext4-fix-bitmap-position-validation.patch
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# Fix exported symbol versions
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bugfix/all/module-disable-matching-missing-version-crc.patch
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