linux-kernel - [PATCH 5.19 120/717] jbd2: fix potential use-after-free in jbd2_fc_wait

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Message-Id: <20221022072436.737549980@linuxfoundation.org>
Date:   Sat, 22 Oct 2022 09:19:59 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, stable@...nel.org,
        Ye Bin <yebin10@...wei.com>, Jan Kara <jack@...e.cz>,
        Theodore Tso <tytso@....edu>
Subject: [PATCH 5.19 120/717] jbd2: fix potential use-after-free in jbd2_fc_wait_bufs

From: Ye Bin <yebin10@...wei.com>

commit 243d1a5d505d0b0460c9af0ad56ed4a56ef0bebd upstream.

In 'jbd2_fc_wait_bufs' use 'bh' after put buffer head reference count
which may lead to use-after-free.
So judge buffer if uptodate before put buffer head reference count.

Cc: stable@...nel.org
Signed-off-by: Ye Bin <yebin10@...wei.com>
Reviewed-by: Jan Kara <jack@...e.cz>
Link: https://lore.kernel.org/r/20220914100812.1414768-3-yebin10@huawei.com
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/jbd2/journal.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -926,16 +926,16 @@ int jbd2_fc_wait_bufs(journal_t *journal
 	for (i = j_fc_off - 1; i >= j_fc_off - num_blks; i--) {
 		bh = journal->j_fc_wbuf[i];
 		wait_on_buffer(bh);
-		put_bh(bh);
-		journal->j_fc_wbuf[i] = NULL;
 		/*
 		 * Update j_fc_off so jbd2_fc_release_bufs can release remain
 		 * buffer head.
 		 */
 		if (unlikely(!buffer_uptodate(bh))) {
-			journal->j_fc_off = i;
+			journal->j_fc_off = i + 1;
 			return -EIO;
 		}
+		put_bh(bh);
+		journal->j_fc_wbuf[i] = NULL;
 	}
 
 	return 0;