[PATCH AUTOSEL 6.14 34/34] ext4: make block validity check resistent to sb bh corruption

Sasha Levin
2025-04-14T13:27:28Z

From: Ojaswin Mujoo <ojaswin@linux.ibm.com>

[ Upstream commit ccad447a3d331a239477c281533bacb585b54a98 ]

Block validity checks need to be skipped in case they are called
for journal blocks since they are part of system's protected
zone.

Currently, this is done by checking inode->ino against
sbi->s_es->s_journal_inum, which is a direct read from the ext4 sb
buffer head. If someone modifies this underneath us then the
s_journal_inum field might get corrupted. To prevent against this,
change the check to directly compare the inode with journal->j_inode.

**Slight change in behavior**: During journal init path,
check_block_validity etc might be called for journal inode when
sbi->s_journal is not set yet. In this case we now proceed with
ext4_inode_block_valid() instead of returning early. Since systems zones
have not been set yet, it is okay to proceed so we can perform basic
checks on the blocks.

Suggested-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://patch.msgid.link/0c06bc9ebfcd6ccfed84a36e79147bf45ff5adc1.1743142920.git.ojaswin@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ext4/block_validity.c | 5 ++---
fs/ext4/inode.c | 7 ++++---
2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c
index 87ee3a17bd29c..e8c5525afc67a 100644
--- a/fs/ext4/block_validity.c
+++ b/fs/ext4/block_validity.c
@@ -351,10 +351,9 @@ int ext4_check_blockref(const char *function, unsigned int line,
{
__le32 *bref = p;
unsigned int blk;
+ journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;

- if (ext4_has_feature_journal(inode->i_sb) &&
- (inode->i_ino ==
- le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_journal_inum)))
+ if (journal && inode == journal->j_inode)
return 0;

while (bref < p+max) {
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 4009f9017a0e9..dd1b0118d65aa 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -383,10 +383,11 @@ static int __check_block_validity(struct inode *inode, const char *func,
unsigned int line,
struct ext4_map_blocks *map)
{
- if (ext4_has_feature_journal(inode->i_sb) &&
- (inode->i_ino ==
- le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_journal_inum)))
+ journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
+
+ if (journal && inode == journal->j_inode)
return 0;
+
if (!ext4_inode_block_valid(inode, map->m_pblk, map->m_len)) {
ext4_error_inode(inode, func, line, map->m_pblk,
"lblock %lu mapped to illegal pblock %llu "
--
2.39.5