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 4CE961FB4 for ; Fri, 3 Feb 2023 10:22:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BF2A3C433D2; Fri, 3 Feb 2023 10:22:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1675419779; bh=0+jcL0cpGh18gP3DGO0pTxKbweqX1ksJ6xgS3QQQsZc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=giNSH+V0tF9YC4KVCHtRpU+dZ4TQ8gQrDOqAj0nn5PA+tN0Q1beG1/cIC7Cp0tZWi Gf1DOYtYkIibtzXOaGJoHDTPA30YqVkITSfPMG9BhegxmJCnV5OL5ddgFt4EfowgJS HqRvsqNCROPcFJHSIDnBhuZcPyDFtybwm5OytxAQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com, Gao Xiang , Siddh Raman Pant , Chao Yu , Sasha Levin Subject: [PATCH 6.1 07/28] erofs/zmap.c: Fix incorrect offset calculation Date: Fri, 3 Feb 2023 11:12:55 +0100 Message-Id: <20230203101010.285433065@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230203101009.946745030@linuxfoundation.org> References: <20230203101009.946745030@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Siddh Raman Pant [ Upstream commit 6acd87d50998ef0afafc441613aeaf5a8f5c9eff ] Effective offset to add to length was being incorrectly calculated, which resulted in iomap->length being set to 0, triggering a WARN_ON in iomap_iter_done(). Fix that, and describe it in comments. This was reported as a crash by syzbot under an issue about a warning encountered in iomap_iter_done(), but unrelated to erofs. C reproducer: https://syzkaller.appspot.com/text?tag=ReproC&x=1037a6b2880000 Kernel config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=e2021a61197ebe02 Dashboard link: https://syzkaller.appspot.com/bug?extid=a8e049cd3abd342936b6 Reported-by: syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com Suggested-by: Gao Xiang Signed-off-by: Siddh Raman Pant Reviewed-by: Gao Xiang Reviewed-by: Chao Yu Link: https://lore.kernel.org/r/20221209102151.311049-1-code@siddh.me Signed-off-by: Gao Xiang Signed-off-by: Sasha Levin --- fs/erofs/zmap.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c index e6d5d7a18fb0..39cc014dba40 100644 --- a/fs/erofs/zmap.c +++ b/fs/erofs/zmap.c @@ -793,12 +793,16 @@ static int z_erofs_iomap_begin_report(struct inode *inode, loff_t offset, iomap->type = IOMAP_HOLE; iomap->addr = IOMAP_NULL_ADDR; /* - * No strict rule how to describe extents for post EOF, yet - * we need do like below. Otherwise, iomap itself will get + * No strict rule on how to describe extents for post EOF, yet + * we need to do like below. Otherwise, iomap itself will get * into an endless loop on post EOF. + * + * Calculate the effective offset by subtracting extent start + * (map.m_la) from the requested offset, and add it to length. + * (NB: offset >= map.m_la always) */ if (iomap->offset >= inode->i_size) - iomap->length = length + map.m_la - offset; + iomap->length = length + offset - map.m_la; } iomap->flags = 0; return 0; -- 2.39.0