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| author | Junrui Luo <moonafterrain@outlook.com> | 2026-05-13 17:28:40 +0800 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2026-06-03 10:24:01 -0400 |
| commit | 289a2ca0c9b7eae74f93fc213b0b971669b8683d (patch) | |
| tree | 0f2a41620a55bdb7c8fb826025735cabb0bbaf04 | |
| parent | 8b3bc93fee6771775243665a0cf31857d6659775 (diff) | |
| download | linux-289a2ca0c9b7eae74f93fc213b0b971669b8683d.tar.gz linux-289a2ca0c9b7eae74f93fc213b0b971669b8683d.zip | |
jbd2: fix integer underflow in jbd2_journal_initialize_fast_commit()
jbd2_journal_initialize_fast_commit() validates journal capacity by
checking (journal->j_last - num_fc_blks < JBD2_MIN_JOURNAL_BLOCKS).
Both j_last and num_fc_blks are unsigned, so when num_fc_blks exceeds
j_last the subtraction wraps to a large value, bypassing the bounds
check.
The resulting underflow corrupts j_last, j_fc_first, and j_free,
leading to journal abort.
Fix by checking num_fc_blks against j_last before the subtraction,
returning -EFSCORRUPTED.
Fixes: 6866d7b3f2bb ("ext4 / jbd2: add fast commit initialization")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
Fixes: e029c5f27987 ("ext4: make num of fast commit blocks configurable")
Reviewed-by: Baokun Li <libaokun@linux.alibaba.com>
Fixes: e029c5f279872 ("ext4: make num of fast commit blocks configurable")
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/SYBPR01MB7881663C927DE9D7BBF4D1DFAF062@SYBPR01MB7881.ausprd01.prod.outlook.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
| -rw-r--r-- | fs/jbd2/journal.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index 4f397fcdb13c..e3b2e38e1a1b 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -2263,6 +2263,8 @@ jbd2_journal_initialize_fast_commit(journal_t *journal) unsigned long long num_fc_blks; num_fc_blks = jbd2_journal_get_num_fc_blks(sb); + if (num_fc_blks > journal->j_last) + return -EFSCORRUPTED; if (journal->j_last - num_fc_blks < JBD2_MIN_JOURNAL_BLOCKS) return -ENOSPC; |