From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.2 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 Received: from second.openwall.net (second.openwall.net [193.110.157.125]) by inbox.vuxu.org (Postfix) with SMTP id D8BDE265B4 for ; Thu, 29 Feb 2024 15:04:05 +0100 (CET) Received: (qmail 1453 invoked by uid 550); 29 Feb 2024 14:00:23 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 1408 invoked from network); 29 Feb 2024 14:00:22 -0000 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.ispras.ru C0D0F40B278E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ispras.ru; s=default; t=1709215431; bh=IX5wMoXk8kSKulBHjfLfdJYdDIMm4Jgtwetdqh46ojA=; h=Date:From:To:Subject:Reply-To:In-Reply-To:References:From; b=bOATXt2Z7yEJn1XE551kva78TI5PnP+O2LMD5yYgvNO32XYS3eZDjdUMQAuTktBNd 25Zluh4rZ6ict3tNju5VlZ761D3fJQqUWMitqP1cTDVqxETYtKPCx1wGpnAuwsM0zq 5Wj4Xst5qitCMmQKqId0CkAFZmXZxOIxRn4H8p2I= MIME-Version: 1.0 Date: Thu, 29 Feb 2024 17:03:51 +0300 From: Alexey Izbyshev To: musl@lists.openwall.com Mail-Followup-To: musl@lists.openwall.com In-Reply-To: <20210525143210.GH2546@brightrain.aerifal.cx> References: <985e15962c164eb3076752d6ee4c05fe@ispras.ru> <20210524203329.GB2546@brightrain.aerifal.cx> <47bc2113ebf931665b6b88795159de2e@ispras.ru> <20210525143210.GH2546@brightrain.aerifal.cx> User-Agent: Roundcube Webmail/1.4.13 Message-ID: <4f0953e3c103fac9cf01059781742644@ispras.ru> X-Sender: izbyshev@ispras.ru Content-Type: multipart/mixed; boundary="=_61eb09cd93365c24ac9ea772e399aca9" Subject: Re: [musl] Potentially infinite loop in posix_spawn'ed child --=_61eb09cd93365c24ac9ea772e399aca9 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; format=flowed On 2021-05-25 17:32, Rich Felker wrote: > On Tue, May 25, 2021 at 09:30:18AM +0300, Alexey Izbyshev wrote: >> On 2021-05-24 23:33, Rich Felker wrote: >> >On Mon, May 24, 2021 at 01:09:21PM +0300, Alexey Izbyshev wrote: >> >>Hi, >> >> >> >>I've noticed the following loop at https://git.musl-libc.org/cgit/musl/tree/src/process/posix_spawn.c#n159: >> >> >> >> exec(args->path, args->argv, args->envp); >> >> ret = -errno; >> >> >> >>fail: >> >> /* Since sizeof errno < PIPE_BUF, the write is atomic. */ >> >> ret = -ret; >> >> if (ret) while (__syscall(SYS_write, p, &ret, sizeof ret) < 0); >> >> _exit(127); >> >> >> >>Is there any reason that write is done in a loop? If SIGPIPE is >> >>blocked or ignored and the parent dies before this point, the child >> >>will spin in it forever. >> > >> >I suppose the special case of EPIPE should be considered here as no >> >need to inform the parent. Are there any other errors that should be >> >treated specially? >> > >> I'm not aware of any other errors that would need treatment. Is this >> loop intended to be a detection/debugging aid in case of an >> unexpected error? > > It's not a debugging aid so much as a guarantee against forward > progress doing the wrong thing (wrongly reporting success to the > parent when the execve failed). I don't think there are any errors > that should be able to happen here aside from EPIPE though, short of > munging with syscall semantics using seccomp or something which is > outside the scope of what could be expected to work correctly. > I've never sent a patch for this, doing it now. Thanks, Alexey --=_61eb09cd93365c24ac9ea772e399aca9 Content-Transfer-Encoding: base64 Content-Type: text/x-diff; name=0001-posix_spawn-fix-child-spinning-on-write-to-a-broken-.patch Content-Disposition: attachment; filename=0001-posix_spawn-fix-child-spinning-on-write-to-a-broken-.patch; size=1426 RnJvbSAzNmVkYTAxZGJlMGEzNWM0YzY1YzM5NDcyM2E3MGMyZDFiNzVlNTkxIE1vbiBTZXAgMTcg MDA6MDA6MDAgMjAwMQpGcm9tOiBBbGV4ZXkgSXpieXNoZXYgPGl6YnlzaGV2QGlzcHJhcy5ydT4K RGF0ZTogVGh1LCAyOSBGZWIgMjAyNCAxNDoxMzoxOCArMDMwMApTdWJqZWN0OiBbUEFUQ0hdIHBv c2l4X3NwYXduOiBmaXggY2hpbGQgc3Bpbm5pbmcgb24gd3JpdGUgdG8gYSBicm9rZW4gcGlwZQpN YWlsLUZvbGxvd3VwLVRvOiBtdXNsQGxpc3RzLm9wZW53YWxsLmNvbQoKQSBjaGlsZCBwcm9jZXNz IGNyZWF0ZWQgYnkgcG9zaXhfc3Bhd24gcmVwb3J0cyBlcnJvcnMgdG8gaXRzIHBhcmVudCB2aWEK YSBwaXBlLCByZXRyeWluZyBpbmZpbml0ZWx5IG9uIGFueSB3cml0ZSBlcnJvciB0byBwcmV2ZW50 IGZhbHNlbHkKcmVwb3J0aW5nIHN1Y2Nlc3MuIElmIHRoZSAob3JpZ2luYWwpIHBhcmVudCBkaWVz IGJlZm9yZSB3cml0ZSBpcwphdHRlbXB0ZWQsIHRoZXJlIGlzIG5vYm9keSB0byByZXBvcnQgdG8s IGJ1dCB0aGUgY2hpbGQgd2lsbCByZW1haW4Kc3R1Y2sgaW4gdGhlIHdyaXRlIGxvb3AgZm9yZXZl ciBpZiBTSUdQSVBFIGlzIGJsb2NrZWQgb3IgaWdub3JlZC4KRml4IHRoaXMgYnkgbm90IHJldHJ5 aW5nIHdyaXRlIGlmIGl0IGZhaWxzIHdpdGggRVBJUEUuCi0tLQogc3JjL3Byb2Nlc3MvcG9zaXhf c3Bhd24uYyB8IDcgKysrKysrLQogMSBmaWxlIGNoYW5nZWQsIDYgaW5zZXJ0aW9ucygrKSwgMSBk ZWxldGlvbigtKQoKZGlmZiAtLWdpdCBhL3NyYy9wcm9jZXNzL3Bvc2l4X3NwYXduLmMgYi9zcmMv cHJvY2Vzcy9wb3NpeF9zcGF3bi5jCmluZGV4IDcyODU1MWIzNjc5Mi4uODI5NDU5OGJiN2UzIDEw MDY0NAotLS0gYS9zcmMvcHJvY2Vzcy9wb3NpeF9zcGF3bi5jCisrKyBiL3NyYy9wcm9jZXNzL3Bv c2l4X3NwYXduLmMKQEAgLTQsNiArNCw3IEBACiAjaW5jbHVkZSA8dW5pc3RkLmg+CiAjaW5jbHVk ZSA8c2lnbmFsLmg+CiAjaW5jbHVkZSA8ZmNudGwuaD4KKyNpbmNsdWRlIDxlcnJuby5oPgogI2lu Y2x1ZGUgPHN5cy93YWl0Lmg+CiAjaW5jbHVkZSAic3lzY2FsbC5oIgogI2luY2x1ZGUgImxvY2su aCIKQEAgLTE1Niw3ICsxNTcsMTEgQEAgc3RhdGljIGludCBjaGlsZCh2b2lkICphcmdzX3ZwKQog ZmFpbDoKIAkvKiBTaW5jZSBzaXplb2YgZXJybm8gPCBQSVBFX0JVRiwgdGhlIHdyaXRlIGlzIGF0 b21pYy4gKi8KIAlyZXQgPSAtcmV0OwotCWlmIChyZXQpIHdoaWxlIChfX3N5c2NhbGwoU1lTX3dy aXRlLCBwLCAmcmV0LCBzaXplb2YgcmV0KSA8IDApOworCWlmIChyZXQpIHsKKwkJaW50IHI7CisJ CWRvIHIgPSBfX3N5c2NhbGwoU1lTX3dyaXRlLCBwLCAmcmV0LCBzaXplb2YgcmV0KTsKKwkJd2hp bGUgKHI8MCAmJiByIT0tRVBJUEUpOworCX0KIAlfZXhpdCgxMjcpOwogfQogCi0tIAoyLjM5LjIK Cg== --=_61eb09cd93365c24ac9ea772e399aca9--