From patchwork Sun Nov 3 17:11:46 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Simon Marchi (Code Review)" X-Patchwork-Id: 35582 Received: (qmail 2412 invoked by alias); 3 Nov 2019 17:11:55 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 2391 invoked by uid 89); 3 Nov 2019 17:11:55 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-21.0 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3 autolearn=ham version=3.3.1 spammy=structures, Never, apparent, inactive X-HELO: mx1.osci.io X-Gerrit-PatchSet: 1 Date: Sun, 3 Nov 2019 12:11:46 -0500 From: "Florian Weimer (Code Review)" To: libc-alpha@sourceware.org Cc: Florian Weimer Message-ID: Auto-Submitted: auto-generated X-Gerrit-MessageType: newchange Subject: [review] Avoid zero-length array at the end of struct link_map [BZ #25097] X-Gerrit-Change-Id: Ic911100730f9124d4ea977ead8e13cee64b84d45 X-Gerrit-Change-Number: 488 X-Gerrit-ChangeURL: X-Gerrit-Commit: 6a771621414cc85f218d6b13c204552afd0294c3 References: Reply-To: fweimer@redhat.com, fweimer@redhat.com, libc-alpha@sourceware.org MIME-Version: 1.0 Content-Disposition: inline User-Agent: Gerrit/3.0.3-75-g9005159e5d Change URL: https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/488 ...................................................................... Avoid zero-length array at the end of struct link_map [BZ #25097] l_audit ends up as an internal array with _rtld_global, and GCC 10 warns about this. This commit does not change the layout of _rtld_global, so it is suitable for backporting. Future changes could allocate more of the audit state dynamically and remove it from always-allocated data structures, to optimize the common case of inactive auditing. Change-Id: Ic911100730f9124d4ea977ead8e13cee64b84d45 Reviewed-by: Carlos O'Donell --- M include/link.h M sysdeps/generic/ldsodefs.h 2 files changed, 23 insertions(+), 12 deletions(-) diff --git a/include/link.h b/include/link.h index 1184201..be52b97 100644 --- a/include/link.h +++ b/include/link.h @@ -325,16 +325,18 @@ size_t l_relro_size; unsigned long long int l_serial; - - /* Audit information. This array apparent must be the last in the - structure. Never add something after it. */ - struct auditstate - { - uintptr_t cookie; - unsigned int bindflags; - } l_audit[0]; }; +/* Information used by audit modules. For most link maps, this data + immediate follows the link map in memory. For the dynamic linker, + it is allocated separately. See link_map_audit_state in + . */ +struct auditstate +{ + uintptr_t cookie; + unsigned int bindflags; +}; + #if __ELF_NATIVE_CLASS == 32 # define symbind symbind32 diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 04b6d17..eb6cbea 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -379,11 +379,12 @@ /* List of search directories. */ EXTERN struct r_search_path_elem *_dl_all_dirs; - /* Structure describing the dynamic linker itself. We need to - reserve memory for the data the audit libraries need. */ + /* Structure describing the dynamic linker itself. */ EXTERN struct link_map _dl_rtld_map; #ifdef SHARED - struct auditstate audit_data[DL_NNS]; + /* Used to store the audit information for the link map of the + dynamic loader. */ + struct auditstate _dl_rtld_auditstate[DL_NNS]; #endif #if defined SHARED && defined _LIBC_REENTRANT \ @@ -1178,7 +1179,15 @@ static inline struct auditstate * link_map_audit_state (struct link_map *l, size_t index) { - return &l->l_audit[index]; + if (l == &GL (dl_rtld_map)) + /* The auditstate array is stored separately. */ + return &GL (dl_rtld_auditstate) [index]; + else + { + /* The auditstate array follows the link map in memory. */ + struct auditstate *base = (struct auditstate *) (l + 1); + return &base[index]; + } } #endif /* SHARED */