From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5C13A2DF138 for ; Tue, 17 Feb 2026 15:59:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771343958; cv=none; b=MLi0hr8ht9eX7XLiaRlpE7bTCJq0vYjz4jWH4LzvIGp9izWBVAsplI2WJgqWE2AzWJiCvFoDoZobeIxRmzaiWc0riEQvcXeLF9YfZcEmkkhJXYYbmxn2ShAg3fijokvrQJxo/P7j3PgeVJcBIfWZwBkQOyCLyy2DDguUfx69s5Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771343958; c=relaxed/simple; bh=M0WlaWmghgexEmp0RZ1sD+dEAdQmfs8DQydrrjL3F6U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SNcAFeiiY8aDcpfVgej9v2u5otUxd4AuSiwVmffp+wcDNbd13CCCsrNZx3DV1hZ0SHDf7fky28SbA3g2mypOHunezOoKM3xTnDZ4YmoPtWSAbVcjYx+hEP3lKVJdmZmNG9XKcVo5WGgYTjHVv2HzBoK0pw6MbUN8BRCSZXQNqM8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iV4Ts1k0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iV4Ts1k0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52AD4C19421; Tue, 17 Feb 2026 15:59:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771343958; bh=M0WlaWmghgexEmp0RZ1sD+dEAdQmfs8DQydrrjL3F6U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iV4Ts1k09lud+u1aOcccXB8Ti5ITkOszJ/dZeSTYpQmeBdPQEkQsKrKsljOJZOkOg BHmKY6Yn3KWbIoQk6WDHvwuxZA2AFQmjUaWQkHcqRmIXFWLJapwJXFNKqJREtMaRsO 7TQQa2GIoKGxku+9lMbbj5ulw8sPxRMUJzF3+cc9Y2Pu2U53weZdi7yvCbdQQ4iFDW K+f6tFQyjkbhvlgwsZQ6fCX3OaAhSMmQIJFOHJMB9YeUP6OflTUr+TwUUJY+0efyfJ MFHKB0Gout2pKo1eCaJN5uHFAI5FkP3h0k4srC1z+ceF1Yy7/0S8x5DyFuvlAzw8Sq fh16p4Eh87Dxw== From: Sasha Levin To: stable@vger.kernel.org Cc: Chao Yu , stable@kernel.org, syzbot+b4444e3c972a7a124187@syzkaller.appspotmail.com, Jaegeuk Kim , Sasha Levin Subject: [PATCH 6.1.y] f2fs: fix to avoid UAF in f2fs_write_end_io() Date: Tue, 17 Feb 2026 10:59:15 -0500 Message-ID: <20260217155915.3750486-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2026021710-numerator-smoking-8f19@gregkh> References: <2026021710-numerator-smoking-8f19@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chao Yu [ Upstream commit ce2739e482bce8d2c014d76c4531c877f382aa54 ] As syzbot reported an use-after-free issue in f2fs_write_end_io(). It is caused by below race condition: loop device umount - worker_thread - loop_process_work - do_req_filebacked - lo_rw_aio - lo_rw_aio_complete - blk_mq_end_request - blk_update_request - f2fs_write_end_io - dec_page_count - folio_end_writeback - kill_f2fs_super - kill_block_super - f2fs_put_super : free(sbi) : get_pages(, F2FS_WB_CP_DATA) accessed sbi which is freed In kill_f2fs_super(), we will drop all page caches of f2fs inodes before call free(sbi), it guarantee that all folios should end its writeback, so it should be safe to access sbi before last folio_end_writeback(). Let's relocate ckpt thread wakeup flow before folio_end_writeback() to resolve this issue. Cc: stable@kernel.org Fixes: e234088758fc ("f2fs: avoid wait if IO end up when do_checkpoint for better performance") Reported-by: syzbot+b4444e3c972a7a124187@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=b4444e3c972a7a124187 Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim [ folio => page ] Signed-off-by: Sasha Levin --- fs/f2fs/data.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index 3bf3b24e38d23..0e13b01db06aa 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -358,14 +358,20 @@ static void f2fs_write_end_io(struct bio *bio) page->index != nid_of_node(page)); dec_page_count(sbi, type); + + /* + * we should access sbi before end_page_writeback() to + * avoid racing w/ kill_f2fs_super() + */ + if (type == F2FS_WB_CP_DATA && !get_pages(sbi, type) && + wq_has_sleeper(&sbi->cp_wait)) + wake_up(&sbi->cp_wait); + if (f2fs_in_warm_node_list(sbi, page)) f2fs_del_fsync_node_entry(sbi, page); clear_page_private_gcing(page); end_page_writeback(page); } - if (!get_pages(sbi, F2FS_WB_CP_DATA) && - wq_has_sleeper(&sbi->cp_wait)) - wake_up(&sbi->cp_wait); bio_put(bio); } -- 2.51.0