From patchwork Wed Dec 2 11:30:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 1409656 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org (client-ip=2620:52:3:1:0:246e:9693:128c; helo=sourceware.org; envelope-from=libc-alpha-bounces@sourceware.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=sourceware.org Authentication-Results: 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=JjxuBTYq; dkim-atps=neutral Received: from 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 RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 4CmGwz2lVsz9sPB for ; Wed, 2 Dec 2020 22:30:27 +1100 (AEDT) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id C31C3385780D; Wed, 2 Dec 2020 11:30:22 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C31C3385780D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1606908622; bh=xkfynwYnPRKHnyjTzBdWL8d+b070YoYAeA+4rCBAQ+o=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:From; b=JjxuBTYqD11H4GIXX4iq3/gEa17MJGSQ6pwtjNzlBJTOms9myHtKad9389RzGDG+e gIY2RvglABXHbIuoeyzYW2pFQYxdjkmYNkwMfkJHqY+sTcWeqNdeB+2jEX5TZf89rP F8XlXg/9/qyyFTfcWH/b9JX1Rqti1TnfTXC5xPNg= 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 [63.128.21.124]) by sourceware.org (Postfix) with ESMTP id 5786E385780D for ; Wed, 2 Dec 2020 11:30:09 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 5786E385780D Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-392-YNTRZXprMS-ZFnKH3DZATg-1; Wed, 02 Dec 2020 06:30:06 -0500 X-MC-Unique: YNTRZXprMS-ZFnKH3DZATg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C6020100F345 for ; Wed, 2 Dec 2020 11:30:05 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-112-44.ams2.redhat.com [10.36.112.44]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1A68C60BFA for ; Wed, 2 Dec 2020 11:30:04 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH v2 1/2] Replace __libc_multiple_libcs with __libc_initial flag Message-Id: Date: Wed, 02 Dec 2020 12:30:03 +0100 User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) 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@sourceware.org Sender: "Libc-alpha" Change sbrk to fail for !__libc_initial (in the generic implementation). As a result, sbrk is (relatively) safe to use for the __libc_initial case (from the main libc). It is therefore no longer necessary to avoid using it in that case (or updating the brk cache), and the __libc_initial flag does not need to be updated as part of dlmopen or static dlopen. As before, direct brk system calls on Linux may lead to memory corruption. Reviewed-by: Adhemerval Zanella --- v2: Switch to a flag with just two states, simplifying the code. Add sbrk blocking for inner libcs. brk can't be changed yet due to the pending refactoring. csu/init-first.c | 10 +++------ csu/libc-start.c | 13 +++++------ elf/dl-open.c | 6 ----- elf/dl-sysdep.c | 2 -- elf/libc_early_init.c | 9 ++++++++ include/libc-internal.h | 7 +++++- misc/sbrk.c | 34 ++++++++++++++++++++--------- sysdeps/mach/hurd/dl-sysdep.c | 2 -- sysdeps/mach/hurd/i386/init-first.c | 10 +++++---- 9 files changed, 53 insertions(+), 40 deletions(-) diff --git a/csu/init-first.c b/csu/init-first.c index 47aaacdbd0..2115215668 100644 --- a/csu/init-first.c +++ b/csu/init-first.c @@ -28,10 +28,6 @@ #include -/* Set nonzero if we have to be prepared for more than one libc being - used in the process. Safe assumption if initializer never runs. */ -int __libc_multiple_libcs attribute_hidden = 1; - /* Remember the command line argument and enviroment contents for later calls of initializers for dynamic libraries. */ int __libc_argc attribute_hidden; @@ -50,16 +46,16 @@ _init_first (int argc, char **argv, char **envp) { #endif - __libc_multiple_libcs = &_dl_starting_up && !_dl_starting_up; - /* Make sure we don't initialize twice. */ - if (!__libc_multiple_libcs) +#ifdef SHARED + if (__libc_initial) { /* Set the FPU control word to the proper default value if the kernel would use a different value. */ if (__fpu_control != GLRO(dl_fpu_control)) __setfpucw (__fpu_control); } +#endif /* Save the command-line arguments. */ __libc_argc = argc; diff --git a/csu/libc-start.c b/csu/libc-start.c index 2d4d2ed1f9..d330812c2d 100644 --- a/csu/libc-start.c +++ b/csu/libc-start.c @@ -141,8 +141,6 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL), /* Result of the 'main' function. */ int result; - __libc_multiple_libcs = &_dl_starting_up && !_dl_starting_up; - #ifndef SHARED _dl_relocate_static_pie (); @@ -213,12 +211,11 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL), # endif # ifdef DL_SYSDEP_OSCHECK - if (!__libc_multiple_libcs) - { - /* This needs to run to initiliaze _dl_osversion before TLS - setup might check it. */ - DL_SYSDEP_OSCHECK (__libc_fatal); - } + { + /* This needs to run to initiliaze _dl_osversion before TLS + setup might check it. */ + DL_SYSDEP_OSCHECK (__libc_fatal); + } # endif /* Initialize libpthread if linked in. */ diff --git a/elf/dl-open.c b/elf/dl-open.c index 8769e47051..6710ea04cd 100644 --- a/elf/dl-open.c +++ b/elf/dl-open.c @@ -787,12 +787,6 @@ dl_open_worker (void *a) if (mode & RTLD_GLOBAL) add_to_global_update (new); -#ifndef SHARED - /* We must be the static _dl_open in libc.a. A static program that - has loaded a dynamic object now has competition. */ - __libc_multiple_libcs = 1; -#endif - /* Let the user know about the opencount. */ if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_FILES)) _dl_debug_printf ("opening file=%s [%lu]; direct_opencount=%u\n\n", diff --git a/elf/dl-sysdep.c b/elf/dl-sysdep.c index 854570821c..6cc4a76560 100644 --- a/elf/dl-sysdep.c +++ b/elf/dl-sysdep.c @@ -58,8 +58,6 @@ ElfW(Addr) _dl_base_addr; #endif int __libc_enable_secure attribute_relro = 0; rtld_hidden_data_def (__libc_enable_secure) -int __libc_multiple_libcs = 0; /* Defining this here avoids the inclusion - of init-first. */ /* This variable contains the lowest stack address ever used. */ void *__libc_stack_end attribute_relro = NULL; rtld_hidden_data_def(__libc_stack_end) diff --git a/elf/libc_early_init.c b/elf/libc_early_init.c index 725ab2f811..28c6adca10 100644 --- a/elf/libc_early_init.c +++ b/elf/libc_early_init.c @@ -18,8 +18,13 @@ #include #include +#include #include +#ifdef SHARED +_Bool __libc_initial; +#endif + void __libc_early_init (_Bool initial) { @@ -28,4 +33,8 @@ __libc_early_init (_Bool initial) /* Only the outer namespace is marked as single-threaded. */ __libc_single_threaded = initial; + +#ifdef SHARED + __libc_initial = initial; +#endif } diff --git a/include/libc-internal.h b/include/libc-internal.h index 915613c030..c1e74056ac 100644 --- a/include/libc-internal.h +++ b/include/libc-internal.h @@ -47,6 +47,11 @@ extern void __init_misc (int, char **, char **) attribute_hidden; extern __typeof (__profile_frequency) __profile_frequency attribute_hidden; # endif -extern int __libc_multiple_libcs attribute_hidden; +#ifdef SHARED +/* True if this libc belongs to the initially loaded program (i.e., it + is not for an audit module, not loaded via dlmopen, and not loaded + via static dlopen either). */ +extern _Bool __libc_initial attribute_hidden; +#endif #endif /* _LIBC_INTERNAL */ diff --git a/misc/sbrk.c b/misc/sbrk.c index ba3322fba6..a6929d736d 100644 --- a/misc/sbrk.c +++ b/misc/sbrk.c @@ -16,9 +16,10 @@ . */ #include +#include +#include #include #include -#include /* Defined in brk.c. */ extern void *__curbrk; @@ -30,21 +31,34 @@ extern int __brk (void *addr); void * __sbrk (intptr_t increment) { - void *oldbrk; - - /* If this is not part of the dynamic library or the library is used - via dynamic loading in a statically linked program update - __curbrk from the kernel's brk value. That way two separate - instances of __brk and __sbrk can share the heap, returning - interleaved pieces of it. */ - if (__curbrk == NULL || __libc_multiple_libcs) + /* Controls whether __brk (0) is called to read the brk value from + the kernel. */ + bool update_brk = __curbrk == NULL; + +#if defined (SHARED) && ! IS_IN (rtld) + if (!__libc_initial) + { + if (increment != 0) + { + /* Do not allow changing the brk from an inner libc because + it cannot be synchronized with the outer libc's brk. */ + __set_errno (ENOMEM); + return (void *) -1; + } + /* Querying the kernel's brk value from an inner namespace is + fine. */ + update_brk = true; + } +#endif + + if (update_brk) if (__brk (0) < 0) /* Initialize the break. */ return (void *) -1; if (increment == 0) return __curbrk; - oldbrk = __curbrk; + void *oldbrk = __curbrk; if (increment > 0 ? ((uintptr_t) oldbrk + (uintptr_t) increment < (uintptr_t) oldbrk) : ((uintptr_t) oldbrk < (uintptr_t) -increment)) diff --git a/sysdeps/mach/hurd/dl-sysdep.c b/sysdeps/mach/hurd/dl-sysdep.c index 370495710e..a5169d85e7 100644 --- a/sysdeps/mach/hurd/dl-sysdep.c +++ b/sysdeps/mach/hurd/dl-sysdep.c @@ -57,8 +57,6 @@ extern char **_environ; int __libc_enable_secure = 0; rtld_hidden_data_def (__libc_enable_secure) -int __libc_multiple_libcs = 0; /* Defining this here avoids the inclusion - of init-first. */ /* This variable contains the lowest stack address ever used. */ void *__libc_stack_end = NULL; rtld_hidden_data_def(__libc_stack_end) diff --git a/sysdeps/mach/hurd/i386/init-first.c b/sysdeps/mach/hurd/i386/init-first.c index 1827479f86..cbbc12204a 100644 --- a/sysdeps/mach/hurd/i386/init-first.c +++ b/sysdeps/mach/hurd/i386/init-first.c @@ -30,6 +30,7 @@ #include #include #include +#include extern void __mach_init (void); extern void __init_misc (int, char **, char **); @@ -40,7 +41,6 @@ unsigned long int __hurd_threadvar_stack_mask; #ifndef SHARED int __libc_enable_secure; #endif -int __libc_multiple_libcs attribute_hidden = 1; extern int __libc_argc attribute_hidden; extern char **__libc_argv attribute_hidden; @@ -56,13 +56,12 @@ DEFINE_HOOK (_hurd_preinit_hook, (void)); static void posixland_init (int argc, char **argv, char **envp) { - __libc_multiple_libcs = &_dl_starting_up && !_dl_starting_up; - /* Now we have relocations etc. we can start signals etc. */ _hurd_libc_proc_init (argv); +#ifdef SHARED /* Make sure we don't initialize twice. */ - if (!__libc_multiple_libcs) + if (__libc_initial) { /* Set the FPU control word to the proper default value. */ __setfpucw (__fpu_control); @@ -72,6 +71,9 @@ posixland_init (int argc, char **argv, char **envp) /* Initialize data structures so the additional libc can do RPCs. */ __mach_init (); } +#else /* !SHARED */ + __setfpucw (__fpu_control); +#endif /* Save the command-line arguments. */ __libc_argc = argc;