From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A4EFC433FE for ; Tue, 8 Dec 2020 23:16:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2EDBA22203 for ; Tue, 8 Dec 2020 23:16:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731704AbgLHXQb (ORCPT ); Tue, 8 Dec 2020 18:16:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725906AbgLHXQb (ORCPT ); Tue, 8 Dec 2020 18:16:31 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC47CC0613D6; Tue, 8 Dec 2020 15:15:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:Content-Type: In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To:Subject:Sender :Reply-To:Content-ID:Content-Description; bh=E+S79NxXtXZvWU7yR5R96CB53fdCfSscjaREn60hxaQ=; b=jt4QRfprixCRm3FoESEGq24COb r3si0Q+hvoW6LRVid49gwZaLRwodTWEoF75Brevquncqim/vh2WVVE1pozmXKaDLgh+ZmejTUCgFk VnDKTMvtTIMIEwGfCGBWrk9raiARMW8amoBrTXhSwG1C5obfEW5DR1DkV0MXbeKNefsGZq5zoB82m UsG7/BX0VR3sOtwbWRqBV4mdJ6acWIWpydIFrXIOUiss8OC80spOmvpdtmr0MbKe1LfYdUgZ2ehQC BUqVX6g/tyxy9xcpYcJb7Vo2mBN+ijqwamn/BGpHtixVcEGXWA0MzQtwOsJ2r8FoiUsf8MyFMubIi zlN6JsVg==; Received: from [2601:1c0:6280:3f0::1494] by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kmmCy-0000dW-1m; Tue, 08 Dec 2020 23:15:48 +0000 Subject: Re: memory leak in generic_parse_monolithic [+PATCH] To: David Howells Cc: syzbot , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk References: <1c752ffe-8118-f9ea-e928-d92783a5c516@infradead.org> <6db2af99-e6e3-7f28-231e-2bdba05ca5fa@infradead.org> <0000000000002a530d05b400349b@google.com> <928043.1607416561@warthog.procyon.org.uk> <1030308.1607468099@warthog.procyon.org.uk> From: Randy Dunlap Message-ID: Date: Tue, 8 Dec 2020 15:15:44 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <1030308.1607468099@warthog.procyon.org.uk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/8/20 2:54 PM, David Howells wrote: > Randy Dunlap wrote: > >>> Now the backtrace only shows what the state was when the string was allocated; >>> it doesn't show what happened to it after that, so another possibility is that >>> the filesystem being mounted nicked what vfs_parse_fs_param() had rightfully >>> stolen, transferring fc->source somewhere else and then failed to release it - >>> most likely on mount failure (ie. it's an error handling bug in the >>> filesystem). >>> >>> Do we know what filesystem it was? >> >> Yes, it's call AFS (or kAFS). > > Hmmm... afs parses the string in afs_parse_source() without modifying it, > then moves the pointer to fc->source (parallelling vfs_parse_fs_param()) and > doesn't touch it again. fc->source should be cleaned up by do_new_mount() > calling put_fs_context() at the end of the function. > > As far as I can tell with the attached print-insertion patch, it works, called > by the following commands, some of which are correct and some which aren't: > > # mount -t afs none /xfstest.test/ -o dyn > # umount /xfstest.test > # mount -t afs "" /xfstest.test/ -o foo > mount: /xfstest.test: bad option; for several filesystems (e.g. nfs, cifs) you might need a /sbin/mount. helper program. > # umount /xfstest.test > umount: /xfstest.test: not mounted. > # mount -t afs %xfstest.test20 /xfstest.test/ -o foo > mount: /xfstest.test: bad option; for several filesystems (e.g. nfs, cifs) you might need a /sbin/mount. helper program. > # umount /xfstest.test > umount: /xfstest.test: not mounted. > # mount -t afs %xfstest.test20 /xfstest.test/ > # umount /xfstest.test > > Do you know if the mount was successful and what the mount parameters were? Here's the syzbot reproducer: https://syzkaller.appspot.com/x/repro.c?x=129ca3d6500000 The "interesting" mount params are: source=%^]$[+%](${:\017k[)-:,source=%^]$[+.](%{:\017\200[)-:,\000 There is no other AFS activity: nothing mounted, no cells known (or whatever that is), etc. I don't recall if the mount was successful and I can't test it just now. My laptop is mucked up. Be aware that this report could just be a false positive: it waits for 5 seconds then looks for a memleak. AFAIK, it's possible that the "leaked" memory is still in valid use and will be freed some day. > David > --- > diff --git a/fs/afs/super.c b/fs/afs/super.c > index 6c5900df6aa5..4c44ec0196c9 100644 > --- a/fs/afs/super.c > +++ b/fs/afs/super.c > @@ -299,7 +299,7 @@ static int afs_parse_source(struct fs_context *fc, struct fs_parameter *param) > ctx->cell = cell; > } > > - _debug("CELL:%s [%p] VOLUME:%*.*s SUFFIX:%s TYPE:%d%s", > + kdebug("CELL:%s [%p] VOLUME:%*.*s SUFFIX:%s TYPE:%d%s", > ctx->cell->name, ctx->cell, > ctx->volnamesz, ctx->volnamesz, ctx->volname, > suffix ?: "-", ctx->type, ctx->force ? " FORCE" : ""); > @@ -318,6 +318,8 @@ static int afs_parse_param(struct fs_context *fc, struct fs_parameter *param) > struct afs_fs_context *ctx = fc->fs_private; > int opt; > > + kenter("%s,%p '%s'", param->key, param->string, param->string); > + > opt = fs_parse(fc, afs_fs_parameters, param, &result); > if (opt < 0) > return opt; > diff --git a/fs/fs_context.c b/fs/fs_context.c > index 2834d1afa6e8..f530a33876ce 100644 > --- a/fs/fs_context.c > +++ b/fs/fs_context.c > @@ -450,6 +450,8 @@ void put_fs_context(struct fs_context *fc) > put_user_ns(fc->user_ns); > put_cred(fc->cred); > put_fc_log(fc); > + if (strcmp(fc->fs_type->name, "afs") == 0) > + printk("PUT %p '%s'\n", fc->source, fc->source); > put_filesystem(fc->fs_type); > kfree(fc->source); > kfree(fc); > @@ -671,6 +673,8 @@ void vfs_clean_context(struct fs_context *fc) > fc->s_fs_info = NULL; > fc->sb_flags = 0; > security_free_mnt_opts(&fc->security); > + if (strcmp(fc->fs_type->name, "afs") == 0) > + printk("CLEAN %p '%s'\n", fc->source, fc->source); > kfree(fc->source); > fc->source = NULL; > > I'll check more after my test machine is working again. thanks. -- ~Randy