[PATCH 01/19] jbd2: Fix possible overflow in jbd2_log_space_left()
From: Jan Kara <jack@suse.cz>
Date: 2019-09-30 10:43:24
Also in:
stable
Subsystem:
journalling layer for block devices (jbd2), the rest · Maintainers:
"Theodore Ts'o", Jan Kara, Linus Torvalds
When number of free space in the journal is very low, the arithmetic in jbd2_log_space_left() could underflow resulting in very high number of free blocks and thus triggering assertion failure in transaction commit code complaining there's not enough space in the journal: J_ASSERT(journal->j_free > 1); Properly check for the low number of free blocks. CC: stable@vger.kernel.org Signed-off-by: Jan Kara <jack@suse.cz> --- include/linux/jbd2.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index df03825ad1a1..b20ef2c0812d 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h@@ -1584,7 +1584,7 @@ static inline int jbd2_space_needed(journal_t *journal) static inline unsigned long jbd2_log_space_left(journal_t *journal) { /* Allow for rounding errors */ - unsigned long free = journal->j_free - 32; + long free = journal->j_free - 32; if (journal->j_committing_transaction) { unsigned long committing = atomic_read(&journal->
@@ -1593,7 +1593,7 @@ static inline unsigned long jbd2_log_space_left(journal_t *journal) /* Transaction + control blocks */ free -= committing + (committing >> JBD2_CONTROL_BLOCKS_SHIFT); } - return free; + return max_t(long, free, 0); } /*
--
2.16.4