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jbd2: Fix possible overflow in jbd2_log_space_left()

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commit add3efdd78b8a0478ce423bb9d4df6bd95e8b335 upstream.

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
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191105164437.32602-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jan Kara 2019-11-05 17:44:07 +01:00 committed by Greg Kroah-Hartman
parent ce624b2089
commit 799a03be21
1 changed files with 2 additions and 2 deletions
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4
include/linux/jbd2.h
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@ -1440,7 +1440,7 @@ 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->
@ -1449,7 +1449,7 @@ 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);
}
/*