linux-ext4 - [PATCH -next 1/2] jbd2: fix potential buffer head reference count leak

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Date:   Wed, 14 Sep 2022 18:08:11 +0800
From:   Ye Bin <yebin10@...wei.com>
To:     <tytso@....edu>, <adilger.kernel@...ger.ca>,
        <linux-ext4@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <jack@...e.cz>,
        Ye Bin <yebin10@...wei.com>
Subject: [PATCH -next 1/2] jbd2: fix potential buffer head reference count leak

As in 'jbd2_fc_wait_bufs' if buffer isn't uptodate, will return -EIO without
update 'journal->j_fc_off'. But 'jbd2_fc_release_bufs' will release buffer head
from ‘j_fc_off - 1’ if 'bh' is NULL will terminal release which will lead to
buffer head buffer head reference count leak.
To solve above issue, update 'journal->j_fc_off' before return -EIO.

Signed-off-by: Ye Bin <yebin10@...wei.com>
---
 fs/jbd2/journal.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 140b070471c0..1c833d8cb0fe 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -925,8 +925,14 @@ int jbd2_fc_wait_bufs(journal_t *journal, int num_blks)
 		wait_on_buffer(bh);
 		put_bh(bh);
 		journal->j_fc_wbuf[i] = NULL;
-		if (unlikely(!buffer_uptodate(bh)))
+		/*
+		 * Update j_fc_off so jbd2_fc_release_bufs can release remain
+		 * buffer head.
+		 */
+		if (unlikely(!buffer_uptodate(bh))) {
+			journal->j_fc_off = i;
 			return -EIO;
+		}
 	}
 
 	return 0;
-- 
2.31.1