From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-x844.google.com (mail-qt1-x844.google.com [IPv6:2607:f8b0:4864:20::844]) by sourceware.org (Postfix) with ESMTPS id A54533857C6B for ; Thu, 6 Aug 2020 19:24:13 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org A54533857C6B Received: by mail-qt1-x844.google.com with SMTP id x12so28730324qtp.1 for ; Thu, 06 Aug 2020 12:24:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:autocrypt:subject :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=Q0wdv+TJbaPMT85iKvlxWUp4eP8E7Vz8iguyAUd417s=; b=mFk/5MVJmMCsenzaNnDRRcVUad+7AG/mmKfpWLRT4/pA7isN1Wt7msCSFJCQYlpUH2 857tZpcVRf95NswRQYA5EUvCeFM7vBpRYXhWUUow+UUJZ8UZ1sIAz+WGSlqudfJJ+VKQ W8oi90vBstTomkz8OBjxPIzwrcYmKgWbvCvZo+JOb/X2WFOZ/6TyiQuu60XJW2DNvIlQ yhgMVSWMJ5KEkMXQ6SB3lSrog9EBfQq0wVl0msbxmlOOrxyQeWCOFznqgwvkJiGb3VY8 D3kL+DFvDPHEeiM9AcjClkR3wMcv1Tp7dje0rP/SMCFOu24PNWIrWDU7cz0VCTt07Bkj 1Wjg== X-Gm-Message-State: AOAM530+f8vc2qd5lpGbmWk0OGl+Pcu4L7guUZB1Z6DyBYgMvP/RJ4QA yZuWEvrngxrmnYeRtu9OK7xYLw== X-Google-Smtp-Source: ABdhPJz+RMBDFAfOOlvjmzys8kL6VJntG84I8rw0Eh+6T7exd5EXvzEWG+s+brYmBrioSLWda/xGsg== X-Received: by 2002:ac8:f15:: with SMTP id e21mr10659597qtk.123.1596741853013; Thu, 06 Aug 2020 12:24:13 -0700 (PDT) Received: from [192.168.1.4] ([177.194.48.209]) by smtp.googlemail.com with ESMTPSA id c205sm4961789qkg.98.2020.08.06.12.24.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Aug 2020 12:24:12 -0700 (PDT) To: Xiaoming Ni , libc-alpha@sourceware.org, glibc-bugs@sourceware.org, carlos@redhat.com Cc: yukeji@huawei.com, wangle6@huawei.com References: <20200806143209.4044-1-nixiaoming@huawei.com> From: Adhemerval Zanella Autocrypt: addr=adhemerval.zanella@linaro.org; prefer-encrypt=mutual; keydata= mQINBFcVGkoBEADiQU2x/cBBmAVf5C2d1xgz6zCnlCefbqaflUBw4hB/bEME40QsrVzWZ5Nq 8kxkEczZzAOKkkvv4pRVLlLn/zDtFXhlcvQRJ3yFMGqzBjofucOrmdYkOGo0uCaoJKPT186L NWp53SACXguFJpnw4ODI64ziInzXQs/rUJqrFoVIlrPDmNv/LUv1OVPKz20ETjgfpg8MNwG6 iMizMefCl+RbtXbIEZ3TE/IaDT/jcOirjv96lBKrc/pAL0h/O71Kwbbp43fimW80GhjiaN2y WGByepnkAVP7FyNarhdDpJhoDmUk9yfwNuIuESaCQtfd3vgKKuo6grcKZ8bHy7IXX1XJj2X/ BgRVhVgMHAnDPFIkXtP+SiarkUaLjGzCz7XkUn4XAGDskBNfbizFqYUQCaL2FdbW3DeZqNIa nSzKAZK7Dm9+0VVSRZXP89w71Y7JUV56xL/PlOE+YKKFdEw+gQjQi0e+DZILAtFjJLoCrkEX w4LluMhYX/X8XP6/C3xW0yOZhvHYyn72sV4yJ1uyc/qz3OY32CRy+bwPzAMAkhdwcORA3JPb kPTlimhQqVgvca8m+MQ/JFZ6D+K7QPyvEv7bQ7M+IzFmTkOCwCJ3xqOD6GjX3aphk8Sr0dq3 4Awlf5xFDAG8dn8Uuutb7naGBd/fEv6t8dfkNyzj6yvc4jpVxwARAQABtElBZGhlbWVydmFs IFphbmVsbGEgTmV0dG8gKExpbmFybyBWUE4gS2V5KSA8YWRoZW1lcnZhbC56YW5lbGxhQGxp bmFyby5vcmc+iQI3BBMBCAAhBQJXFRpKAhsDBQsJCAcDBRUKCQgLBRYCAwEAAh4BAheAAAoJ EKqx7BSnlIjv0e8P/1YOYoNkvJ+AJcNUaM5a2SA9oAKjSJ/M/EN4Id5Ow41ZJS4lUA0apSXW NjQg3VeVc2RiHab2LIB4MxdJhaWTuzfLkYnBeoy4u6njYcaoSwf3g9dSsvsl3mhtuzm6aXFH /Qsauav77enJh99tI4T+58rp0EuLhDsQbnBic/ukYNv7sQV8dy9KxA54yLnYUFqH6pfH8Lly sTVAMyi5Fg5O5/hVV+Z0Kpr+ZocC1YFJkTsNLAW5EIYSP9ftniqaVsim7MNmodv/zqK0IyDB GLLH1kjhvb5+6ySGlWbMTomt/or/uvMgulz0bRS+LUyOmlfXDdT+t38VPKBBVwFMarNuREU2 69M3a3jdTfScboDd2ck1u7l+QbaGoHZQ8ZNUrzgObltjohiIsazqkgYDQzXIMrD9H19E+8fw kCNUlXxjEgH/Kg8DlpoYJXSJCX0fjMWfXywL6ZXc2xyG/hbl5hvsLNmqDpLpc1CfKcA0BkK+ k8R57fr91mTCppSwwKJYO9T+8J+o4ho/CJnK/jBy1pWKMYJPvvrpdBCWq3MfzVpXYdahRKHI ypk8m4QlRlbOXWJ3TDd/SKNfSSrWgwRSg7XCjSlR7PNzNFXTULLB34sZhjrN6Q8NQZsZnMNs TX8nlGOVrKolnQPjKCLwCyu8PhllU8OwbSMKskcD1PSkG6h3r0AquQINBFcVGkoBEACgAdbR Ck+fsfOVwT8zowMiL3l9a2DP3Eeak23ifdZG+8Avb/SImpv0UMSbRfnw/N81IWwlbjkjbGTu oT37iZHLRwYUFmA8fZX0wNDNKQUUTjN6XalJmvhdz9l71H3WnE0wneEM5ahu5V1L1utUWTyh VUwzX1lwJeV3vyrNgI1kYOaeuNVvq7npNR6t6XxEpqPsNc6O77I12XELic2+36YibyqlTJIQ V1SZEbIy26AbC2zH9WqaKyGyQnr/IPbTJ2Lv0dM3RaXoVf+CeK7gB2B+w1hZummD21c1Laua +VIMPCUQ+EM8W9EtX+0iJXxI+wsztLT6vltQcm+5Q7tY+HFUucizJkAOAz98YFucwKefbkTp eKvCfCwiM1bGatZEFFKIlvJ2QNMQNiUrqJBlW9nZp/k7pbG3oStOjvawD9ZbP9e0fnlWJIsj 6c7pX354Yi7kxIk/6gREidHLLqEb/otuwt1aoMPg97iUgDV5mlNef77lWE8vxmlY0FBWIXuZ yv0XYxf1WF6dRizwFFbxvUZzIJp3spAao7jLsQj1DbD2s5+S1BW09A0mI/1DjB6EhNN+4bDB SJCOv/ReK3tFJXuj/HbyDrOdoMt8aIFbe7YFLEExHpSk+HgN05Lg5TyTro8oW7TSMTk+8a5M kzaH4UGXTTBDP/g5cfL3RFPl79ubXwARAQABiQIfBBgBCAAJBQJXFRpKAhsMAAoJEKqx7BSn lIjvI/8P/jg0jl4Tbvg3B5kT6PxJOXHYu9OoyaHLcay6Cd+ZrOd1VQQCbOcgLFbf4Yr+rE9l mYsY67AUgq2QKmVVbn9pjvGsEaz8UmfDnz5epUhDxC6yRRvY4hreMXZhPZ1pbMa6A0a/WOSt AgFj5V6Z4dXGTM/lNManr0HjXxbUYv2WfbNt3/07Db9T+GZkpUotC6iknsTA4rJi6u2ls0W9 1UIvW4o01vb4nZRCj4rni0g6eWoQCGoVDk/xFfy7ZliR5B+3Z3EWRJcQskip/QAHjbLa3pml xAZ484fVxgeESOoaeC9TiBIp0NfH8akWOI0HpBCiBD5xaCTvR7ujUWMvhsX2n881r/hNlR9g fcE6q00qHSPAEgGr1bnFv74/1vbKtjeXLCcRKk3Ulw0bY1OoDxWQr86T2fZGJ/HIZuVVBf3+ gaYJF92GXFynHnea14nFFuFgOni0Mi1zDxYH/8yGGBXvo14KWd8JOW0NJPaCDFJkdS5hu0VY 7vJwKcyHJGxsCLU+Et0mryX8qZwqibJIzu7kUJQdQDljbRPDFd/xmGUFCQiQAncSilYOcxNU EMVCXPAQTteqkvA+gNqSaK1NM9tY0eQ4iJpo+aoX8HAcn4sZzt2pfUB9vQMTBJ2d4+m/qO6+ cFTAceXmIoFsN8+gFN3i8Is3u12u8xGudcBPvpoy4OoG Subject: Re: [PATCH] stdlib: realpath use malloc replace __alloca to reduce stack overflow risks [BZ #26341] Message-ID: Date: Thu, 6 Aug 2020 16:24:09 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200806143209.4044-1-nixiaoming@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-14.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, 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: 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-List-Received-Date: Thu, 06 Aug 2020 19:24:15 -0000 On 06/08/2020 11:32, Xiaoming Ni wrote: > Realpath() cyclically invokes __alloca() when processing soft link files, > which may consume 164 KB stack space. > Therefore, replace __alloca with malloc to reduce stack overflow risks > > Signed-off-by: Xiaoming Ni We do not use SCO, but rather copyright assignments (Carlos can check if your is ok with FSF). If possible could you provide a testcase? Maybe by limiting the stack with getrlimit and using the example provided in the bugzilla? Patch look ok, just formatting style nits. As a side note, for Linux we could simplify the realpath implementation a *lot* with limited stack size and no malloc allocation we could remove the GNU extension to return prefix of path that is not readable or does not exist if resolved_path is not NULL (is a GNU extension that came from the implementation itself that works directly on the buffer). > --- > stdlib/canonicalize.c | 28 +++++++++++++++++++++++++--- > 1 file changed, 25 insertions(+), 3 deletions(-) > > diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c > index cbd885a3c5..d3130d81f0 100644 > --- a/stdlib/canonicalize.c > +++ b/stdlib/canonicalize.c > @@ -163,27 +163,46 @@ __realpath (const char *name, char *resolved) > > if (S_ISLNK (st.st_mode)) > { > - char *buf = __alloca (path_max); > + char *buf = malloc (path_max); > size_t len; > > + if (!buf) Use explicit check (buf != NULL). > + { > + __set_errno (ENOMEM); > + goto error; > + } > + > if (++num_links > __eloop_threshold ()) > { > __set_errno (ELOOP); > + free(buf); Space after free. > goto error; > } > > n = __readlink (rpath, buf, path_max - 1); > if (n < 0) > - goto error; > + { > + free(buf); Ditto. > + goto error; > + } > buf[n] = '\0'; > > if (!extra_buf) > - extra_buf = __alloca (path_max); > + { > + extra_buf = malloc (path_max); > + if (!extra_buf) Use explicit check (extra_buf != NULL). > + { > + free(buf); Space after free. > + __set_errno (ENOMEM); > + goto error; > + } > + } > > len = strlen (end); > if (path_max - n <= len) > { > __set_errno (ENAMETOOLONG); > + free(buf); Ditto. > goto error; > } > > @@ -197,6 +216,7 @@ __realpath (const char *name, char *resolved) > /* Back up to previous component, ignore if at root already: */ > if (dest > rpath + 1) > while ((--dest)[-1] != '/'); > + free(buf); Ditto. > } > else if (!S_ISDIR (st.st_mode) && *end != '\0') > { > @@ -210,12 +230,14 @@ __realpath (const char *name, char *resolved) > *dest = '\0'; > > assert (resolved == NULL || resolved == rpath); > + free(extra_buf); > return rpath; > > error: > assert (resolved == NULL || resolved == rpath); > if (resolved == NULL) > free (rpath); > + free(extra_buf); Space after free. > return NULL; > } > libc_hidden_def (__realpath) >