From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 413F23857711 for ; Tue, 4 Jul 2023 20:02:44 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 413F23857711 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1688500963; 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=Mz39Tf0o4FOiiHCOT6Zg+9kCmon6Ea/s68RvjWWOW3Q=; b=Wy9FAEcsecTrcaGDhtacd9xUJnv8mLQo8K+ObVqDUnDaj5gQXhs7c0RqeOW0sQZXDiQi66 GNPppUxGMoYDvnm1Pd2nTsH/44Y7VLJsTJGLNctHXm47+9KSTla6F+1tWiKaDRm8RMHIzz kL9swvqq5E5+bCb6R7r6H2FZbrq86n0= 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-510-NQfKLKA1MxiUZOjoWD4rzQ-1; Tue, 04 Jul 2023 16:02:43 -0400 X-MC-Unique: NQfKLKA1MxiUZOjoWD4rzQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BC1BC8022EF for ; Tue, 4 Jul 2023 20:02:42 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.2.16.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1FC8115230A6 for ; Tue, 4 Jul 2023 20:02:41 +0000 (UTC) From: Florian Weimer To: libc-alpha@sourceware.org Subject: [PATCH 06/33] elf: Remove version assert in check_match in elf/dl-lookup.c In-Reply-To: Message-ID: References: X-From-Line: da4784766111c520e107c351490ae2bb14be61fe Mon Sep 17 00:00:00 2001 Date: Tue, 04 Jul 2023 22:02:40 +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 10.11.54.7 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-10.5 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 List-Id: 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; } -- 2.41.0