From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.8 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id D928A1F4B5 for ; Tue, 12 Nov 2019 09:22:36 +0000 (UTC) DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:date:message-id :mime-version:content-type; q=dns; s=default; b=e03SyQg1S18JH6jN bMR/OwS5tAWGph7/pJW/omoaxkShZUI3s5X5Of71fmws4KYKTjvalYdVk8irETY2 +j2KYeS15qzjQ3btYb3Lb5X0+pjyzq/63rp8AEFUyiR8qv2fLnNORlz4F3R//VgY bDcIF4293TyFnrvlXdmDVv1TPl4= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:date:message-id :mime-version:content-type; s=default; bh=QDMcEw/y5ycp9dmj8FRXtH eYE5w=; b=OLQIlfQfsJNcJbbGJVNgniW7vwUxwqe5FPx3k45z9l1c87Lp6Pm0dc sXfc2kO1iWlL3vHLT8W6Z+0xLgad1VNnrc0DO93yX4pUA2DKZZKee4xDMJrIJbg1 p6VzugPbZVrOvvDqH6QMrgAOnnLnqeBYCrhhelGJKwn6sIrSmVZyY= Received: (qmail 24525 invoked by alias); 12 Nov 2019 09:22:20 -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 Received: (qmail 24511 invoked by uid 89); 12 Nov 2019 09:22:20 -0000 Authentication-Results: sourceware.org; auth=none X-HELO: huawei.com From: Liusirui To: CC: , , , , Subject: [PATCH] fix null pointer in mtrace Date: Tue, 12 Nov 2019 17:22:19 +0800 Message-ID: <1573550539-34259-1-git-send-email-liusirui@huawei.com> MIME-Version: 1.0 Content-Type: text/plain In a multi-threaded program, some threads request or free memory and try to write trace info into file which "mallstream" points to. At the same time, another thread calls "muntrace" and set "mallstream" to NULL. This may cause a segmentation fault. The comment in malloc/mtrace.c says "We could be printing a NULL here; that's OK.". Although the functions mtrace/muntrace are used for debugging, program isn't expected to crash while using these functions. --- malloc/mtrace.c | 29 ++++++++++++++++------------- 1 file changed, 16 insertions(+), 13 deletions(-) diff --git a/malloc/mtrace.c b/malloc/mtrace.c index 707f998..33f01b4 100644 --- a/malloc/mtrace.c +++ b/malloc/mtrace.c @@ -44,6 +44,10 @@ #define TRACE_BUFFER_SIZE 512 +#define mtrace_print(file, format, ...) do { \ +if (file != NULL) mtrace_print(file, format,##__VA_ARGS__); \ +} while(0) + static FILE *mallstream; static const char mallenv[] = "MALLOC_TRACE"; static char *malloc_trace_buffer; @@ -99,12 +103,12 @@ tr_where (const void *caller, Dl_info *info) ")"); } - fprintf (mallstream, "@ %s%s%s[%p] ", + mtrace_print (mallstream, "@ %s%s%s[%p] ", info->dli_fname ? : "", info->dli_fname ? ":" : "", buf, caller); } else - fprintf (mallstream, "@ [%p] ", caller); + mtrace_print (mallstream, "@ [%p] ", caller); } } @@ -166,7 +170,7 @@ tr_freehook (void *ptr, const void *caller) Dl_info *info = lock_and_info (caller, &mem); tr_where (caller, info); /* Be sure to print it first. */ - fprintf (mallstream, "- %p\n", ptr); + mtrace_print (mallstream, "- %p\n", ptr); if (ptr == mallwatch) { __libc_lock_unlock (lock); @@ -198,8 +202,7 @@ tr_mallochook (size_t size, const void *caller) set_trace_hooks (); tr_where (caller, info); - /* We could be printing a NULL here; that's OK. */ - fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size); + mtrace_print (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size); __libc_lock_unlock (lock); @@ -232,17 +235,17 @@ tr_reallochook (void *ptr, size_t size, const void *caller) { if (size != 0) /* Failed realloc. */ - fprintf (mallstream, "! %p %#lx\n", ptr, (unsigned long int) size); + mtrace_print (mallstream, "! %p %#lx\n", ptr, (unsigned long int) size); else - fprintf (mallstream, "- %p\n", ptr); + mtrace_print (mallstream, "- %p\n", ptr); } else if (ptr == NULL) - fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size); + mtrace_print (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size); else { - fprintf (mallstream, "< %p\n", ptr); + mtrace_print (mallstream, "< %p\n", ptr); tr_where (caller, info); - fprintf (mallstream, "> %p %#lx\n", hdr, (unsigned long int) size); + mtrace_print (mallstream, "> %p %#lx\n", hdr, (unsigned long int) size); } __libc_lock_unlock (lock); @@ -270,7 +273,7 @@ tr_memalignhook (size_t alignment, size_t size, const void *caller) tr_where (caller, info); /* We could be printing a NULL here; that's OK. */ - fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size); + mtrace_print (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size); __libc_lock_unlock (lock); @@ -333,7 +336,7 @@ mtrace (void) /* Be sure it doesn't malloc its buffer! */ malloc_trace_buffer = mtb; setvbuf (mallstream, malloc_trace_buffer, _IOFBF, TRACE_BUFFER_SIZE); - fprintf (mallstream, "= Start\n"); + mtrace_print (mallstream, "= Start\n"); save_default_hooks (); set_trace_hooks (); #ifdef _LIBC @@ -363,6 +366,6 @@ muntrace (void) mallstream = NULL; set_default_hooks (); - fprintf (f, "= End\n"); + mtrace_print (f, "= End\n"); fclose (f); } -- 2.7.4