From nobody Tue Sep 16 17:48:02 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1D3CFC4167B for ; Fri, 30 Dec 2022 15:43:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235276AbiL3Pnt (ORCPT ); Fri, 30 Dec 2022 10:43:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56468 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235425AbiL3Pnm (ORCPT ); Fri, 30 Dec 2022 10:43:42 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA1B71B9F1 for ; Fri, 30 Dec 2022 07:43:41 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 968E5B81CC2 for ; Fri, 30 Dec 2022 15:43:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 47014C433D2; Fri, 30 Dec 2022 15:43:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1672415019; bh=MApoGiLoefSH4r+JR0/qNkucbn2OhIB8DVcH1zXvi+Y=; h=From:To:Cc:Subject:Date:From; b=dphRm1ggz5v5Qt0dr9xZHKVqpoJYqh+TqKT0mwChf9iJ0DXpweo8sWg6BglnJC6UG WWx/5ujniUx/QKMwjspaDHwCG3nd0P3RGZzNYG1W5vz8zI36ncnLPRIXcpUPtigKr/ CO43Bi/z41So2x/cU5Kd/dbcy3Rprh/oUzvEmmwxfY9VglK6Q6Swa75R/O28/gZs4L jASNVmrE4/tpLv4hsiV04XJZhqxK/FngemZnGvLgo9jReq34kcej0OftJ3/7WgxAE2 byqABOKT/GhBA3BmdFzQpk5JbY+07d9I+C1zd7fJ9Yo89i8KLCz1K0OJr72wXK9LpH yeUCiuANGj0xg== From: Chao Yu To: jaegeuk@kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Chao Yu Subject: [PATCH] f2fs: fix to avoid NULL pointer dereference in f2fs_issue_flush() Date: Fri, 30 Dec 2022 23:43:32 +0800 Message-Id: <20221230154332.5082-1-chao@kernel.org> X-Mailer: git-send-email 2.36.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" With below two cases, it will cause NULL pointer dereference when accessing SM_I(sbi)->fcc_info in f2fs_issue_flush(). a) If kthread_run() fails in f2fs_create_flush_cmd_control(), it will release SM_I(sbi)->fcc_info, - mount -o noflush_merge /dev/vda /mnt/f2fs - mount -o remount,flush_merge /dev/vda /mnt/f2fs -- kthread_run() fails - dd if=3D/dev/zero of=3D/mnt/f2fs/file bs=3D4k count=3D1 conv=3Dfsync b) we will never allocate memory for SM_I(sbi)->fcc_info w/ below testcase, - mount -o ro /dev/vda /mnt/f2fs - mount -o rw,remount /dev/vda /mnt/f2fs - dd if=3D/dev/zero of=3D/mnt/f2fs/file bs=3D4k count=3D1 conv=3Dfsync In order to fix this issue, let change as below: - fix error path handling in f2fs_create_flush_cmd_control(). - allocate SM_I(sbi)->fcc_info even if readonly is on. Signed-off-by: Chao Yu --- fs/f2fs/segment.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 2646575f43de..16f60c646cc2 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -663,8 +663,7 @@ int f2fs_create_flush_cmd_control(struct f2fs_sb_info *= sbi) if (IS_ERR(fcc->f2fs_issue_flush)) { int err =3D PTR_ERR(fcc->f2fs_issue_flush); =20 - kfree(fcc); - SM_I(sbi)->fcc_info =3D NULL; + fcc->f2fs_issue_flush =3D NULL; return err; } =20 @@ -5137,11 +5136,9 @@ int f2fs_build_segment_manager(struct f2fs_sb_info *= sbi) =20 init_f2fs_rwsem(&sm_info->curseg_lock); =20 - if (!f2fs_readonly(sbi->sb)) { - err =3D f2fs_create_flush_cmd_control(sbi); - if (err) - return err; - } + err =3D f2fs_create_flush_cmd_control(sbi); + if (err) + return err; =20 err =3D create_discard_cmd_control(sbi); if (err) --=20 2.36.1