From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 93901 invoked by alias); 11 Aug 2017 15:31:35 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 92485 invoked by uid 89); 11 Aug 2017 15:30:26 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-24.1 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,RCVD_IN_DNSWL_NONE,RCVD_IN_SORBS_SPAM,SEM_URIRED,SPF_PASS autolearn=ham version=3.3.2 spammy=Hx-languages-length:2311 X-HELO: mail-oi0-f65.google.com Received: from mail-oi0-f65.google.com (HELO mail-oi0-f65.google.com) (209.85.218.65) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Fri, 11 Aug 2017 15:30:24 +0000 Received: by mail-oi0-f65.google.com with SMTP id q70so3626631oic.2 for ; Fri, 11 Aug 2017 08:30:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=cc0dITpQ4CC30NI7bxrWe6kNRvhYMWheOST9my5Oph8=; b=tVO8zCPleTqnL439U2DG9f44XOMi1NvkWtFElhfCabZJpuZTPeqOWVZ9B/p1LmPVBk 8GPUjZkQfRuUfj7UgzUIQeFx8x7+wIQAacFqS86QmNvbA4sRzRZNHAfliGwkNV7Z02zf lj8I8RWa0JQlJJmRlO2qBl31idFeuDipcICB4OUPdM8FRxL8pWG5A1s8BxBYKkytHJR4 EAVGKAf3T6OkDVAQ+wnNiMoBy881MoeQ57QZdwcgMyIr6CTzAt50qfrNzJp6xqVvYtJX zzfwu+lODPllrj6CX6Vv/AuAJLlhLJ+krNwX6MtaXjhXV6GTKKbWqeJ9oH9vN6qQoetC z+9Q== X-Gm-Message-State: AHYfb5jQYlZtyqmqetDAfPJeCFXn5XHXKmxS8h7PFo8G9+Q4CIVBMTuD 0Lhu/eweOcI1tG7dKiXsyoBskrQhWA== X-Received: by 10.202.179.85 with SMTP id c82mr16888298oif.5.1502465422077; Fri, 11 Aug 2017 08:30:22 -0700 (PDT) MIME-Version: 1.0 Received: by 10.74.136.75 with HTTP; Fri, 11 Aug 2017 08:30:21 -0700 (PDT) In-Reply-To: <20170811092709.GH8039@1170ee0b50d5> References: <20170811092709.GH8039@1170ee0b50d5> From: "H.J. Lu" Date: Fri, 11 Aug 2017 15:31:00 -0000 Message-ID: Subject: Re: Synthetic symbol leak in in elf_x86_64_get_synthetic_symtab and elf_read_minimal_symbols To: Yao Qi Cc: Alex Lindsay , GDB Content-Type: text/plain; charset="UTF-8" X-IsSubscribed: yes X-SW-Source: 2017-08/txt/msg00240.txt.bz2 On Fri, Aug 11, 2017 at 2:27 AM, Yao Qi wrote: > On 17-08-07 10:19:15, Alex Lindsay wrote: >> >> We perform a couple of dynamic allocations in >> elf_x86_64_get_synthetic_symtab (elf64-x86-64.c): >> >> s = *ret = (asymbol *) bfd_zmalloc (size); >> >> names = (char *) bfd_malloc (size); >> >> that appear to never get freed. My patch for this: > > Good catch! It is more complicated that other bfd targets allocate > memory for asymbol in a different way as if asymbol.name is defined > as an zero-length array, so memory allocated for both asymbol and .name > in one bfd_malloc call, like, > > sym = *r->sym_ptr_ptr; > if (!sym_exists_at (syms, opdsymend, symcount, > sym->section->id, sym->value + r->addend)) > { > ++count; > size += sizeof (asymbol); > size += strlen (syms[i]->name) + 2; > } > } > > if (size == 0) > goto done; > s = *ret = bfd_malloc (size); > > or > > size = count * sizeof (asymbol); > p = relplt->relocation; > for (i = 0; i < count; i++, p += elf32_arm_size_info.int_rels_per_ext_rel) > { > size += strlen ((*p->sym_ptr_ptr)->name) + sizeof ("@plt"); > if (p->addend != 0) > size += sizeof ("+0x") - 1 + 8; > } > > s = *ret = (asymbol *) bfd_malloc (size); > >> >> diff --git a/gdb/elfread.c b/gdb/elfread.c >> index ece704ca7c..5ed8a6f957 100644 >> --- a/gdb/elfread.c >> +++ b/gdb/elfread.c >> @@ -1144,6 +1144,9 @@ elf_read_minimal_symbols (struct objfile *objfile, int >> symfile_flags, >> >> if (symtab_create_debug) >> fprintf_unfiltered (gdb_stdlog, "Done reading minimal symbols.\n"); >> + if (synthcount > 0) >> + xfree ((char *) synthsyms->name); > > We can't do this for some bfd targets. > >> + xfree (synthsyms); > > We can only safely do this, but .name is leaked for x86_64. Other > tools using bfd, like objdump, nm, and gprof may have this issue too. > I'll ask binutils people on asymbol allocation and de-allocation. > This is: https://sourceware.org/bugzilla/show_bug.cgi?id=21943 i386 and x86-64 get_synthetic_symtab don't know if @plt should be added to symbol name for a PLT entry. The first pass checks if @plt is needed and extra space is allocated in the second pass. We can assume @plt is needed and waste some space if it isn't. -- H.J.