linux-kernel - [PATCH AUTOSEL 5.15 15/15] ext4: make block validity check resistent to sb bh corruption

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Message-Id: <20250414133126.680846-15-sashal@kernel.org>
Date: Mon, 14 Apr 2025 09:31:25 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
	Baokun Li <libaokun1@...wei.com>,
	Jan Kara <jack@...e.cz>,
	Zhang Yi <yi.zhang@...wei.com>,
	Theodore Ts'o <tytso@....edu>,
	Sasha Levin <sashal@...nel.org>,
	adilger.kernel@...ger.ca,
	linux-ext4@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 15/15] ext4: make block validity check resistent to sb bh corruption

From: Ojaswin Mujoo <ojaswin@...ux.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@...wei.com>
Reviewed-by: Baokun Li <libaokun1@...wei.com>
Reviewed-by: Jan Kara <jack@...e.cz>
Reviewed-by: Zhang Yi <yi.zhang@...wei.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Link: https://patch.msgid.link/0c06bc9ebfcd6ccfed84a36e79147bf45ff5adc1.1743142920.git.ojaswin@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Sasha Levin <sashal@...nel.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 6fe3c941b5651..4d6ba140276b5 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 87e6187e6584b..88992594b4724 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -409,10 +409,11 @@ 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