From patchwork Fri Sep 6 11:13:15 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 13794050 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 91CCBCD5BDD for ; Fri, 6 Sep 2024 11:27:23 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1smX03-0001HA-Qh; Fri, 06 Sep 2024 07:19:35 -0400 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 1smX02-000143-8k; Fri, 06 Sep 2024 07:19:34 -0400 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 1smX00-0008Mg-68; Fri, 06 Sep 2024 07:19:33 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id CA3EE8C4B3; Fri, 6 Sep 2024 14:12:10 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id D71F813371C; Fri, 6 Sep 2024 14:13:28 +0300 (MSK) Received: (nullmailer pid 353762 invoked by uid 1000); Fri, 06 Sep 2024 11:13:25 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Richard Henderson , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , Michael Tokarev Subject: [Stable-9.0.3 66/69] linux-user: Handle short reads in mmap_h_gt_g Date: Fri, 6 Sep 2024 14:13:15 +0300 Message-Id: <20240906111324.353230-66-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass 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_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Richard Henderson In particular, if an image has a large bss, we can hit EOF before reading all host_len bytes of the mapping. Create a helper, mmap_pread to handle the job for both the larger block in mmap_h_gt_g itself, as well as the smaller block in mmap_frag. Cc: qemu-stable@nongnu.org Fixes: eb5027ac618 ("linux-user: Split out mmap_h_gt_g") Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2504 Signed-off-by: Richard Henderson Message-Id: <20240820050848.165253-2-richard.henderson@linaro.org> Reviewed-by: Philippe Mathieu-Daudé (cherry picked from commit a4ad4a9d98f7fbde806f07da21e69f39e134cdf1) Signed-off-by: Michael Tokarev diff --git a/linux-user/mmap.c b/linux-user/mmap.c index 2a11d921ab..9e94f36ba2 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -282,6 +282,40 @@ static int do_munmap(void *addr, size_t len) return munmap(addr, len); } +/* + * Perform a pread on behalf of target_mmap. We can reach EOF, we can be + * interrupted by signals, and in general there's no good error return path. + * If @zero, zero the rest of the block at EOF. + * Return true on success. + */ +static bool mmap_pread(int fd, void *p, size_t len, off_t offset, bool zero) +{ + while (1) { + ssize_t r = pread(fd, p, len, offset); + + if (likely(r == len)) { + /* Complete */ + return true; + } + if (r == 0) { + /* EOF */ + if (zero) { + memset(p, 0, len); + } + return true; + } + if (r > 0) { + /* Short read */ + p += r; + len -= r; + offset += r; + } else if (errno != EINTR) { + /* Error */ + return false; + } + } +} + /* * Map an incomplete host page. * @@ -356,10 +390,9 @@ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last, /* Read or zero the new guest pages. */ if (flags & MAP_ANONYMOUS) { memset(g2h_untagged(start), 0, last - start + 1); - } else { - if (pread(fd, g2h_untagged(start), last - start + 1, offset) == -1) { - return false; - } + } else if (!mmap_pread(fd, g2h_untagged(start), last - start + 1, + offset, true)) { + return false; } /* Put final protection */ @@ -852,8 +885,7 @@ static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len, } if (misaligned_offset) { - /* TODO: The read could be short. */ - if (pread(fd, p, host_len, offset + real_start - start) != host_len) { + if (!mmap_pread(fd, p, host_len, offset + real_start - start, false)) { do_munmap(p, host_len); return -1; }