From patchwork Thu Dec 7 10:31:30 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 81635 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 72AA638618EC for ; Thu, 7 Dec 2023 10:31:58 +0000 (GMT) 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 8E278385AE43 for ; Thu, 7 Dec 2023 10:31:34 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 8E278385AE43 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com ARC-Filter: OpenARC Filter v1.0.0 sourceware.org 8E278385AE43 Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1701945095; cv=none; b=aA2H+f7c5GkZxufRLezd7E9vgfcFPliDItGTRAk1bDAJYchoA8IqjVocEAmzHDZhH3w42fK5SscQlYcWypGMZqxj/iZt5e6klqxUduP0wpddJPwdTAmraxWToEYCalWwM9Pu0u/VCZliAtlAv6D12NFoX1jsQNfIBYwRQCGuxIY= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1701945095; c=relaxed/simple; bh=nhhwm2u7KHGPHTMpQU1GcsFIsJXlLOcRezzIeAwUwU0=; h=DKIM-Signature:From:To:Subject:Message-ID:Date:MIME-Version; b=AjyE5KF37jyH6NyQbF4XfFTll59uA6+j+SunIN4S8E35CCzl5zSNkfezGBlYu6st2oqJ+qfoHtBMT1w+el3MzMZKT0pqPijI9AHXMk+EgDfHBDMkm8LlXcORRJaFtnXOh7hHR2NNDP8vr+o6RPzWr5B8j12MCqa2+pSYbMkmvlI= ARC-Authentication-Results: i=1; server2.sourceware.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1701945094; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Bera5ZRSj/BapXKQZu/i1l5AxcGKdB5+hdT70BSdn/o=; b=CVQgKEm5B1IotvJa5P4EnSUBjOwKYOLD/aJB0H9DtcKjv37onyJrCdGY4Ek05Hh1m+C523 /ZIffp39laEBFc4ArpHiy88kWM9zOQjlaxO5FeOw2yNC07751MBYy7+4Yvh6//SwOSiUjX 2yiVDv/q/BBO22H1LGJlm3kGhMrIL/4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-413-wh-MKdiTMvaUozYuorgK_w-1; Thu, 07 Dec 2023 05:31:32 -0500 X-MC-Unique: wh-MKdiTMvaUozYuorgK_w-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A6ED683BA88 for ; Thu, 7 Dec 2023 10:31:32 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.131]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2333E2026D66 for ; Thu, 7 Dec 2023 10:31:31 +0000 (UTC) From: Florian Weimer To: libc-alpha@sourceware.org Subject: [PATCH v3 06/32] elf: Remove version assert in check_match in elf/dl-lookup.c In-Reply-To: Message-ID: <945deda1fb427bf69e06f9f160a1f378f5832581.1701944612.git.fweimer@redhat.com> References: X-From-Line: 945deda1fb427bf69e06f9f160a1f378f5832581 Mon Sep 17 00:00:00 2001 Date: Thu, 07 Dec 2023 11:31:30 +0100 User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 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: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org 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 692c9a47ad..65f910f0e5 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 69c91bea05..f889473378 100644 --- a/elf/dl-lookup.c +++ b/elf/dl-lookup.c @@ -93,22 +93,9 @@ 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; }