From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DA96933DEC2 for ; Thu, 23 Jul 2026 17:22:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784827344; cv=none; b=dr5uvqaLYcXzBIkm7nyB+eb/EEOYp6xvxFgpFBFIQCFWMKDCbFbAU04inYZCrEwrMC/hciDOyLGtlnJbK2Z0WPisqRNJ67Ye9QjayRLs5h/eFpE+LnA+mR4n2Soby+wJDdhGfXAbFswJSDZXRYr1TpDQw6stPiJkKzD1dALKsC0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784827344; c=relaxed/simple; bh=NNmCrPM5GfQCyupYHuuyA8041n/stchphgYukmDAnJw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IMeibBjVNLcW29O0+spmmPN0RgBC2u79iTsjPcgjKnG1NGTxR1qBnqJkebds9RYGy0fBbHycrgCUqSavh27tvcELtY6L6D/mAku8Cif1CAjqwv+E+D3M3GqkdUbBkYShEACpwfav4Fg/hLhG6PPaDrAi3mEMwZABIyJ6L08kPFo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 832421F00A3D; Thu, 23 Jul 2026 17:22:21 +0000 (UTC) From: Sasha Levin To: stable@vger.kernel.org Cc: Junrui Luo , Yuhao Jiang , Baokun Li , Zhang Yi , Jan Kara , Theodore Ts'o , Sasha Levin Subject: [PATCH 5.10.y 2/2] jbd2: fix integer underflow in jbd2_journal_initialize_fast_commit() Date: Thu, 23 Jul 2026 13:22:01 -0400 Message-ID: <20260723172201.3413360-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260723172201.3413360-1-sashal@kernel.org> References: <2026072041-pork-untapped-b293@gregkh> <20260723172201.3413360-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Junrui Luo [ Upstream commit 289a2ca0c9b7eae74f93fc213b0b971669b8683d ] 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 Cc: stable@vger.kernel.org Signed-off-by: Junrui Luo Fixes: e029c5f27987 ("ext4: make num of fast commit blocks configurable") Reviewed-by: Baokun Li Fixes: e029c5f279872 ("ext4: make num of fast commit blocks configurable") Reviewed-by: Zhang Yi Reviewed-by: Jan Kara Link: https://patch.msgid.link/SYBPR01MB7881663C927DE9D7BBF4D1DFAF062@SYBPR01MB7881.ausprd01.prod.outlook.com Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/jbd2/journal.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index cbf56b18521666..526d2971f12e5e 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -2116,6 +2116,8 @@ 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; -- 2.53.0