From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca (simark.ca [158.69.221.121]) by sourceware.org (Postfix) with ESMTPS id 2F7DE3857C46 for ; Tue, 8 Sep 2020 02:21:50 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 2F7DE3857C46 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=simark.ca Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=simark@simark.ca Received: from [10.0.0.11] (173-246-6-90.qc.cable.ebox.net [173.246.6.90]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by simark.ca (Postfix) with ESMTPSA id A6CBC1E509; Mon, 7 Sep 2020 22:21:49 -0400 (EDT) Subject: Re: [PATCH v2 08/10] Avoid double free in startup_inferior To: Kamil Rytarowski , gdb-patches@sourceware.org Cc: tom@tromey.com References: <20200904002905.13616-1-n54@gmx.com> <20200904002905.13616-9-n54@gmx.com> <96629e3b-c2d5-f705-f469-f5e527aab2a2@simark.ca> <0a7f8dbb-a48f-0fc9-77f8-a03c2efe3444@netbsd.org> From: Simon Marchi Message-ID: Date: Mon, 7 Sep 2020 22:21:49 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <0a7f8dbb-a48f-0fc9-77f8-a03c2efe3444@netbsd.org> Content-Type: text/plain; charset=utf-8 Content-Language: fr Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-9.8 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, NICE_REPLY_A, SPF_HELO_PASS, 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: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 Sep 2020 02:21:51 -0000 On 2020-09-07 8:54 p.m., Kamil Rytarowski wrote: > On 07.09.2020 21:19, Simon Marchi wrote: >> On 2020-09-03 8:29 p.m., Kamil Rytarowski wrote: >>> Do not free the last execd pathname as it will be used in >>> prepare_resume_reply(), after attaching a client side. >> >> Ok, so this function returns to its caller the last waitstatus. So indeed we >> want to clean up all the watstatus objects except the last one, which we hand >> over to the caller. >> >>> gdb/ChangeLog: >>> >>> * fork-inferior.c (startup_inferior): Avoid double free. >>> --- >>> gdb/ChangeLog | 4 ++++ >>> gdb/nat/fork-inferior.c | 5 ++++- >>> 2 files changed, 8 insertions(+), 1 deletion(-) >>> >>> diff --git a/gdb/ChangeLog b/gdb/ChangeLog >>> index b96e7bf08e8..1013f6a0b3c 100644 >>> --- a/gdb/ChangeLog >>> +++ b/gdb/ChangeLog >>> @@ -1,3 +1,7 @@ >>> +2020-09-04 Kamil Rytarowski >>> + >>> + * fork-inferior.c (startup_inferior): Avoid double free. >>> + >>> 2020-09-04 Kamil Rytarowski >>> >>> * netbsd-nat.h (netbsd_nat::qxfer_siginfo): Add. >>> diff --git a/gdb/nat/fork-inferior.c b/gdb/nat/fork-inferior.c >>> index 1185ef8998b..94ab0b9cbc2 100644 >>> --- a/gdb/nat/fork-inferior.c >>> +++ b/gdb/nat/fork-inferior.c >>> @@ -526,7 +526,10 @@ startup_inferior (process_stratum_target *proc_target, pid_t pid, int ntraps, >>> >>> case TARGET_WAITKIND_EXECD: >>> /* Handle EXEC signals as if they were SIGTRAP signals. */ >>> - xfree (ws.value.execd_pathname); >>> + /* Do not free the last execd pathname as it will be used in >>> + prepare_resume_reply(), after attaching a client side. */ >> >> Since this is common code, let's just write it in a gdbserver or gdb agnostic way. >> >> I'd suggest something like: Free the exec'ed pathname, but only if this isn't the >> waitstatus we are returning to the caller. >> > > Please be more specific how to fix. Sorry, I just meant "write the comment in a gdbserver of gdb agnostic way". In particular, don't mention prepare_resume_reply, which is gdbserver-specific (whereas the code is shared. I suggest using the phrasing above for the comment. Simon