From patchwork Fri Jul 7 18:47:59 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 1805023 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org (client-ip=2620:52:3:1:0:246e:9693:128c; helo=server2.sourceware.org; envelope-from=libc-alpha-bounces+incoming=patchwork.ozlabs.org@sourceware.org; receiver=) Authentication-Results: legolas.ozlabs.org; dkim=pass (1024-bit key; secure) header.d=sourceware.org header.i=@sourceware.org header.a=rsa-sha256 header.s=default header.b=A4CWRWzk; dkim-atps=neutral Received: from server2.sourceware.org (server2.sourceware.org [IPv6:2620:52:3:1:0:246e:9693:128c]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-384) server-digest SHA384) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4QyMrV4F8fz20ZC for ; Sat, 8 Jul 2023 04:49:30 +1000 (AEST) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 96E46386C5B4 for ; Fri, 7 Jul 2023 18:49:28 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 96E46386C5B4 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1688755768; bh=Mz39Tf0o4FOiiHCOT6Zg+9kCmon6Ea/s68RvjWWOW3Q=; h=To:Subject:In-Reply-To:References:Date:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=A4CWRWzkAvd+s2SnvvY8kqRK7j6ItlhJSmYA4VbJ//+pSm+svckifeWmN2KXs7eVT n3CwZnVSDzIrlwJQW/rljPmcMDwL8OhoWbdtokG2BrHLZuw70f3l2VJ0z+dZCQ2r3t LniWaAQeav5BkyuWxmL1w4Wdur06cXzYZlq3sRBM= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 820A7386C48C for ; Fri, 7 Jul 2023 18:48:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 820A7386C48C Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-457-Pfdrp6lUOhmb4U6-PmA1Xw-1; Fri, 07 Jul 2023 14:48:02 -0400 X-MC-Unique: Pfdrp6lUOhmb4U6-PmA1Xw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BC3C28564EF for ; Fri, 7 Jul 2023 18:48:01 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.2.16.31]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 515D6492B01 for ; Fri, 7 Jul 2023 18:48:01 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH v2 06/32] elf: Remove version assert in check_match in elf/dl-lookup.c In-Reply-To: Message-ID: <6abcd5145b4eb8a4fe7ee2a0640303c2906f8656.1688741159.git.fweimer@redhat.com> References: X-From-Line: 6abcd5145b4eb8a4fe7ee2a0640303c2906f8656 Mon Sep 17 00:00:00 2001 Date: Fri, 07 Jul 2023 20:47:59 +0200 User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-10.6 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Florian Weimer via Libc-alpha From: Florian Weimer Reply-To: Florian Weimer Errors-To: libc-alpha-bounces+incoming=patchwork.ozlabs.org@sourceware.org Sender: "Libc-alpha" This case is detected early in the elf/dl-versionc.c consistency checks. (These checks could be disabled in the future to allow the removal of symbol versioning from objects.) Commit f0b2132b35 ("ld.so: Support moving versioned symbols between sonames [BZ #24741]) removed another call to _dl_name_match_p. The _dl_check_caller function no longer exists, and the remaining calls to _dl_name_match_p happen under the loader lock. This means that atomic accesses are no longer required for the l_libname list. This supersedes commit 395be7c218 ("elf: Fix data race in _dl_name_match_p [BZ #21349]"). --- elf/dl-load.c | 18 +----------------- elf/dl-lookup.c | 19 +++---------------- elf/dl-misc.c | 4 +--- 3 files changed, 5 insertions(+), 36 deletions(-) diff --git a/elf/dl-load.c b/elf/dl-load.c index 58c5dc7355..9a9cee599d 100644 --- a/elf/dl-load.c +++ b/elf/dl-load.c @@ -439,23 +439,7 @@ add_name_to_object (struct link_map *l, const char *name) newname->name = memcpy (newname + 1, name, name_len); newname->next = NULL; newname->dont_free = 0; - /* CONCURRENCY NOTES: - - Make sure the initialization of newname happens before its address is - read from the lastp->next store below. - - GL(dl_load_lock) is held here (and by other writers, e.g. dlclose), so - readers of libname_list->next (e.g. _dl_check_caller or the reads above) - can use that for synchronization, however the read in _dl_name_match_p - may be executed without holding the lock during _dl_runtime_resolve - (i.e. lazy symbol resolution when a function of library l is called). - - The release MO store below synchronizes with the acquire MO load in - _dl_name_match_p. Other writes need to synchronize with that load too, - however those happen either early when the process is single threaded - (dl_main) or when the library is unloaded (dlclose) and the user has to - synchronize library calls with unloading. */ - atomic_store_release (&lastp->next, newname); + lastp->next = newname; } /* Standard search directories. */ diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c index a8f48fed12..52decf616d 100644 --- a/elf/dl-lookup.c +++ b/elf/dl-lookup.c @@ -94,22 +94,9 @@ check_match (const char *const undef_name, const ElfW(Half) *verstab = map->l_versyms; if (version != NULL) { - if (__glibc_unlikely (verstab == NULL)) - { - /* We need a versioned symbol but haven't found any. If - this is the object which is referenced in the verneed - entry it is a bug in the library since a symbol must - not simply disappear. - - It would also be a bug in the object since it means that - the list of required versions is incomplete and so the - tests in dl-version.c haven't found a problem.*/ - assert (version->filename == NULL - || ! _dl_name_match_p (version->filename, map)); - - /* Otherwise we accept the symbol. */ - } - else + /* If there is no version information, accept the symbol. This + can happen during symbol interposition. */ + if (__glibc_likely (verstab != NULL)) { /* We can match the version information or use the default one if it is not hidden. */ diff --git a/elf/dl-misc.c b/elf/dl-misc.c index 5b84adc2f4..e998083284 100644 --- a/elf/dl-misc.c +++ b/elf/dl-misc.c @@ -75,9 +75,7 @@ _dl_name_match_p (const char *name, const struct link_map *map) if (strcmp (name, runp->name) == 0) return 1; else - /* Synchronize with the release MO store in add_name_to_object. - See CONCURRENCY NOTES in add_name_to_object in dl-load.c. */ - runp = atomic_load_acquire (&runp->next); + runp = runp->next; return 0; }