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Message-Id: <20191219183219.496834979@linuxfoundation.org>
Date: Thu, 19 Dec 2019 19:32:44 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Theodore Tso <tytso@....edu>,
Jan Kara <jack@...e.cz>
Subject: [PATCH 4.9 082/199] jbd2: Fix possible overflow in jbd2_log_space_left()
From: Jan Kara <jack@...e.cz>
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@...r.kernel.org
Reviewed-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Jan Kara <jack@...e.cz>
Link: https://lore.kernel.org/r/20191105164437.32602-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
include/linux/jbd2.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1560,7 +1560,7 @@ static inline int jbd2_space_needed(jour
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->
@@ -1569,7 +1569,7 @@ static inline unsigned long jbd2_log_spa
/* Transaction + control blocks */
free -= committing + (committing >> JBD2_CONTROL_BLOCKS_SHIFT);
}
- return free;
+ return max_t(long, free, 0);
}
/*
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