From nobody Wed May 15 18:59:38 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1671218572505109.06069706942696; Fri, 16 Dec 2022 11:22:52 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1p6GHw-0005NS-Bh; Fri, 16 Dec 2022 14:22:32 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1p6GHr-0005ME-69 for qemu-devel@nongnu.org; Fri, 16 Dec 2022 14:22:29 -0500 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1p6GHp-0001xZ-6k for qemu-devel@nongnu.org; Fri, 16 Dec 2022 14:22:26 -0500 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 6AAA5401E9; Fri, 16 Dec 2022 22:22:23 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id CCBB53B9; Fri, 16 Dec 2022 22:22:21 +0300 (MSK) Received: (nullmailer pid 2881948 invoked by uid 1000); Fri, 16 Dec 2022 19:22:21 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org, Laurent Vivier Cc: Michael Tokarev Subject: [PATCH] linux-user: ppoll: eliminate large alloca Date: Fri, 16 Dec 2022 22:22:20 +0300 Message-Id: <20221216192220.2881898-1-mjt@msgid.tls.msk.ru> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: none client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1671218576159100001 Content-Type: text/plain; charset="utf-8" do_ppoll() in linux-user/syscall.c uses alloca() to allocate an array of struct pullfds on the stack. The only upper boundary for number of entries for this array is so that whole thing fits in INT_MAX. But this is definitely too much for a stack allocation. Use heap allocation when large number of entries is requested (currently 128, arbitrary), and continue to use alloca() for smaller allocations, to optimize small operations for small sizes. This, together with previous patch for getgroups(), eliminates all large on-stack allocations from qemu-user/syscall.c. What's left are actually small ones. While at it, also fix missing unlock_user() in two places, and consolidate target_to_host_timespec*() calls into time64?_timespec():_timespec64() construct. Signed-off-by: Michael Tokarev --- linux-user/syscall.c | 50 ++++++++++++++++++++++---------------------- 1 file changed, 25 insertions(+), 25 deletions(-) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 24b25759be..b45690b10a 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -1558,14 +1558,12 @@ static abi_long do_pselect6(abi_long arg1, abi_long= arg2, abi_long arg3, static abi_long do_ppoll(abi_long arg1, abi_long arg2, abi_long arg3, abi_long arg4, abi_long arg5, bool ppoll, bool ti= me64) { - struct target_pollfd *target_pfd; + struct target_pollfd *target_pfd =3D NULL; unsigned int nfds =3D arg2; - struct pollfd *pfd; + struct pollfd *pfd =3D NULL, *heap_pfd =3D NULL; unsigned int i; abi_long ret; =20 - pfd =3D NULL; - target_pfd =3D NULL; if (nfds) { if (nfds > (INT_MAX / sizeof(struct target_pollfd))) { return -TARGET_EINVAL; @@ -1576,7 +1574,16 @@ static abi_long do_ppoll(abi_long arg1, abi_long arg= 2, abi_long arg3, return -TARGET_EFAULT; } =20 - pfd =3D alloca(sizeof(struct pollfd) * nfds); + if (nfds <=3D 128) { + pfd =3D alloca(sizeof(struct pollfd) * nfds); + } else { + heap_pfd =3D g_try_new(struct pollfd, nfds); + if (!heap_pfd) { + ret =3D -TARGET_ENOMEM; + goto out; + } + pfd =3D heap_pfd; + } for (i =3D 0; i < nfds; i++) { pfd[i].fd =3D tswap32(target_pfd[i].fd); pfd[i].events =3D tswap16(target_pfd[i].events); @@ -1587,16 +1594,11 @@ static abi_long do_ppoll(abi_long arg1, abi_long ar= g2, abi_long arg3, sigset_t *set =3D NULL; =20 if (arg3) { - if (time64) { - if (target_to_host_timespec64(timeout_ts, arg3)) { - unlock_user(target_pfd, arg1, 0); - return -TARGET_EFAULT; - } - } else { - if (target_to_host_timespec(timeout_ts, arg3)) { - unlock_user(target_pfd, arg1, 0); - return -TARGET_EFAULT; - } + if (time64 + ? target_to_host_timespec64(timeout_ts, arg3) + : target_to_host_timespec(timeout_ts, arg3)) { + ret =3D -TARGET_EFAULT; + goto out; } } else { timeout_ts =3D NULL; @@ -1605,8 +1607,7 @@ static abi_long do_ppoll(abi_long arg1, abi_long arg2= , abi_long arg3, if (arg4) { ret =3D process_sigsuspend_mask(&set, arg4, arg5); if (ret !=3D 0) { - unlock_user(target_pfd, arg1, 0); - return ret; + goto out; } } =20 @@ -1617,14 +1618,11 @@ static abi_long do_ppoll(abi_long arg1, abi_long ar= g2, abi_long arg3, finish_sigsuspend_mask(ret); } if (!is_error(ret) && arg3) { - if (time64) { - if (host_to_target_timespec64(arg3, timeout_ts)) { - return -TARGET_EFAULT; - } - } else { - if (host_to_target_timespec(arg3, timeout_ts)) { - return -TARGET_EFAULT; - } + if (time64 + ? host_to_target_timespec64(arg3, timeout_ts) + : host_to_target_timespec(arg3, timeout_ts)) { + ret =3D -TARGET_EFAULT; + goto out; } } } else { @@ -1647,6 +1645,8 @@ static abi_long do_ppoll(abi_long arg1, abi_long arg2= , abi_long arg3, target_pfd[i].revents =3D tswap16(pfd[i].revents); } } +out: + g_free(heap_pfd); unlock_user(target_pfd, arg1, sizeof(struct target_pollfd) * nfds); return ret; } --=20 2.30.2