[PATCH v2] jbd2: gate checksum calculations on crc driver presence, not sb flags

Darrick J. Wong
2015-10-03T03:46:27Z

Change the journal's checksum functions to gate on whether or not the
crc32c driver is loaded, and gate the loading on the superblock bits.
This prevents a journal crash if someone loads a journal in no-csum
mode and then randomizes the superblock, thus flipping on the feature
bits.

v2: Create a feature-test helper, use it everywhere.

Tested-By: Nikolay Borisov <kernel@kyup.com>
Reported-by: Nikolay Borisov <kernel@kyup.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/jbd2/journal.c | 6 +++---
include/linux/jbd2.h | 13 +++++++++----
2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 8270fe9..00f7dbd 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -124,7 +124,7 @@ EXPORT_SYMBOL(__jbd2_debug);
/* Checksumming functions */
static int jbd2_verify_csum_type(journal_t *j, journal_superblock_t *sb)
{
- if (!jbd2_journal_has_csum_v2or3(j))
+ if (!jbd2_journal_has_csum_v2or3_feature(j))
return 1;

return sb->s_checksum_type == JBD2_CRC32C_CHKSUM;
@@ -1531,7 +1531,7 @@ static int journal_get_superblock(journal_t *journal)
goto out;
}

- if (jbd2_journal_has_csum_v2or3(journal) &&
+ if (jbd2_journal_has_csum_v2or3_feature(journal) &&
JBD2_HAS_COMPAT_FEATURE(journal, JBD2_FEATURE_COMPAT_CHECKSUM)) {
/* Can't have checksum v1 and v2 on at the same time! */
printk(KERN_ERR "JBD2: Can't enable checksumming v1 and v2/3 "
@@ -1545,7 +1545,7 @@ static int journal_get_superblock(journal_t *journal)
}

/* Load the checksum driver */
- if (jbd2_journal_has_csum_v2or3(journal)) {
+ if (jbd2_journal_has_csum_v2or3_feature(journal)) {
journal->j_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
if (IS_ERR(journal->j_chksum_driver)) {
printk(KERN_ERR "JBD2: Cannot load crc32c driver.\n");
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index df07e78..6da6f89 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1338,13 +1338,18 @@ static inline int tid_geq(tid_t x, tid_t y)
extern int jbd2_journal_blocks_per_page(struct inode *inode);
extern size_t journal_tag_bytes(journal_t *journal);

+static inline bool jbd2_journal_has_csum_v2or3_feature(journal_t *j)
+{
+ return JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2) ||
+ JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V3);
+}
+
static inline int jbd2_journal_has_csum_v2or3(journal_t *journal)
{
- if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_CSUM_V2) ||
- JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_CSUM_V3))
- return 1;
+ WARN_ON_ONCE(jbd2_journal_has_csum_v2or3_feature(journal) &&
+ journal->j_chksum_driver == NULL);

- return 0;
+ return journal->j_chksum_driver != NULL;
}

/*