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Date: Fri, 4 Oct 2019 00:05:47 +0200 From: Jan Kara <jack@...e.cz> To: <linux-ext4@...r.kernel.org> Cc: Ted Tso <tytso@....edu>, Jan Kara <jack@...e.cz>, stable@...r.kernel.org Subject: [PATCH 01/22] jbd2: Fix possible overflow in jbd2_log_space_left() 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@...r.kernel.org Signed-off-by: Jan Kara <jack@...e.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 603fbc4e2f70..10e6049c0ba9 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -1582,7 +1582,7 @@ 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-> @@ -1591,7 +1591,7 @@ 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
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