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[71.206.142.238]) by smtp.gmail.com with ESMTPSA id qf2-20020a0562144b8200b0062621e3b511sm4866237qvb.74.2023.06.01.07.55.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Jun 2023 07:55:02 -0700 (PDT) To: libc-alpha@sourceware.org Cc: Joe Simmons-Talbott Subject: [PATCH v2] check_native: Get rid of alloca Date: Thu, 1 Jun 2023 10:55:00 -0400 Message-Id: <20230601145500.2039369-1-josimmon@redhat.com> X-Mailer: git-send-email 2.40.0 MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.4 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, 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: Joe Simmons-Talbott via Libc-alpha From: Joe Simmons-Talbott Reply-To: Joe Simmons-Talbott Errors-To: libc-alpha-bounces+incoming=patchwork.ozlabs.org@sourceware.org Sender: "Libc-alpha" Use malloc rather than alloca to avoid potential stack overflow. Reviewed-by: Adhemerval Zanella --- Changes to v1: * Do not use a cleanup handler. sysdeps/unix/sysv/linux/check_native.c | 35 ++++++++------------------ 1 file changed, 11 insertions(+), 24 deletions(-) diff --git a/sysdeps/unix/sysv/linux/check_native.c b/sysdeps/unix/sysv/linux/check_native.c index 34876ca624..601f14e5b0 100644 --- a/sysdeps/unix/sysv/linux/check_native.c +++ b/sysdeps/unix/sysv/linux/check_native.c @@ -48,11 +48,20 @@ __check_native (uint32_t a1_index, int *a1_native, nladdr.nl_family = AF_NETLINK; socklen_t addr_len = sizeof (nladdr); - bool use_malloc = false; if (fd < 0) return; + /* Netlink requires that user buffer needs to be either 8kb or page size + (whichever is bigger), however this has been changed over time and now + 8Kb is sufficient (check NLMSG_DEFAULT_SIZE on Linux + linux/include/linux/netlink.h). */ + const size_t buf_size = 8192; + char *buf = malloc (buf_size); + + if (buf == NULL) + goto out; + if (__bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) != 0 || __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) != 0) goto out; @@ -81,26 +90,6 @@ __check_native (uint32_t a1_index, int *a1_native, memset (&nladdr, '\0', sizeof (nladdr)); nladdr.nl_family = AF_NETLINK; -#ifdef PAGE_SIZE - /* Help the compiler optimize out the malloc call if PAGE_SIZE - is constant and smaller or equal to PTHREAD_STACK_MIN/4. */ - const size_t buf_size = PAGE_SIZE; -#else - const size_t buf_size = __getpagesize (); -#endif - char *buf; - - if (__libc_use_alloca (buf_size)) - buf = alloca (buf_size); - else - { - buf = malloc (buf_size); - if (buf != NULL) - use_malloc = true; - else - goto out; - } - struct iovec iov = { buf, buf_size }; if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0, @@ -170,7 +159,5 @@ __check_native (uint32_t a1_index, int *a1_native, out: __close_nocancel_nostatus (fd); - - if (use_malloc) - free (buf); + free(buf); }