From patchwork Wed Jul 19 15:52:31 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Helge Deller X-Patchwork-Id: 13319145 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 03E0DC0015E for ; Wed, 19 Jul 2023 15:53:47 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qM9Ty-00072K-59; Wed, 19 Jul 2023 11:52:54 -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 1qM9Tw-00070Y-5g; Wed, 19 Jul 2023 11:52:52 -0400 Received: from mout.gmx.net ([212.227.15.19]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qM9Tt-0006Ph-NV; Wed, 19 Jul 2023 11:52:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.de; s=s31663417; t=1689781957; x=1690386757; i=deller@gmx.de; bh=efVESnAW6H7a8ZymmHelPG4JpfCKaU44b+i4/YpA37k=; h=X-UI-Sender-Class:From:To:Cc:Subject:Date:In-Reply-To:References; b=gIz+3yIxdFbiIKTyacrbDX9wwLMoWCSAFgm0qZy1TnIYo3wJ11BW15dDFxfB1okVDNrzoyH NJuISt8tpK174S8/EyaTZbtC6I5vktVHpNn5uv+IYDKIKkvjflmlDR97JT/FRt6BfsG4V7f+6 V+7d4ypMQV4AbXtoGBvwBvrcHgoEi6vo8bjSuKq9LoAJ2GVD15lPogPtAlLZZ6IVnVOCI5Z38 Z7QANSeyuYFclZi885/gv7gT95u25aJw7DoRChV/Cn3Qw2KStwEQmal/FwJZ+QNjPZgzeqvA8 6mfXn7KJGMPXCO47Wzq35SOGAgv7HBfDNQjtG9q9+p/FdIw0aAkg== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from p100.fritz.box ([94.134.145.157]) by mail.gmx.net (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1McH5a-1plzmT2ExQ-00cgbC; Wed, 19 Jul 2023 17:52:37 +0200 From: Helge Deller To: Richard Henderson , Laurent Vivier , Andreas Schwab , Michael Tokarev , qemu-devel@nongnu.org Cc: Helge Deller , "Markus F.X.J. Oberhumer" , qemu-stable@nongnu.org Subject: [PULL 1/5] linux-user: Fix qemu brk() to not zero bytes on current page Date: Wed, 19 Jul 2023 17:52:31 +0200 Message-ID: <20230719155235.244478-2-deller@gmx.de> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230719155235.244478-1-deller@gmx.de> References: <20230719155235.244478-1-deller@gmx.de> MIME-Version: 1.0 X-Provags-ID: V03:K1:9ki5GeoyYFsDmXulyMlR7W48fzzEaB85Bx6bs6KtGYaneKENyCU eVOokJLxVu9yJYhwrWuA+yTgatY5rTYxcbNWozvoK0iepV7sEJQP6U+vu3hEo4heZd9XinK plSu+Ad9wDmr/i6tJLEw/1mg1vlllGET6z3k8hLAWAhMuPusBJseR+V5KaTxFruKC3HZx2l gigu35h0sXys34uLrVtxQ== UI-OutboundReport: notjunk:1;M01:P0:NdG3xE/qhxI=;Oi3/a6d/YL3rRDXPdA6e7l6CDTN p4FOj0pjPf9UO3AZ6roKgdsoGwVEdzwNmSh1p38AGCwPhPo0jUNHLd3EBjKVAHnr32mw6sq3+ ps3+YXNWblIuWYMuZO2EdZ/cn6cuLv7+vyrpwfwX/eejnO3Z5ahBgWZOkHEmikY2NcNEL8G2w hVUP3CXyEsdymeuT8GKo8TaolPELECHDyK5AZeimY/Q5VPzobVh5soZBP4/TDUiKPmUrgDKNJ OKcglEGC8oup71IJw2Srf6Xw09kyed9UpyoWx2QOb7NyZJ/pHn5Yr5lxLbeOXA4b57f2IB6yz bOtjJ7LOk1z7n4PbohY+Vt/+Idr9XtwinJAm+m5alIy5IQHH0gZaf+Ro5sgEEFhLjfkpv91fM FBYRPEKZGlI4HhFRwP4fLPIqB1oJzXm/c+N6HKJ7rDDtXcH3VTrrVMMNzfnuVkTZwBfONvLOU NwjhSu0rgIj+PYp9fQ1l6o2dDN0O4JVOZ5zIpNR/pgZu1Fyf3/pD8ZiiNBk62IvlIoWXrq+IQ g/VdHWVYjjTEYCN0ScdGZmqTvh1nKVLmD77LRp0cPIQroQglr6Hs3W4iIzX6FdzrmL+TET/s+ m54nsfKZFN8+kYWcIKsmFZqwgmY4qeMV2YQnToA3+lmVeYWOPT3OsjHF4zH0iJKE0m2rHTkmE zIgK+3TIbBQ0YvO5sOZIgfbkM9X078dM249wB9nLXiucDF9lZzqkVcEBfIkH+AOS7yqmt0DY/ hFzAfUESgnsj/rNglBtiBvfumorc+xqTMh/k/necczyH9JdsdXOpXwMCEWtUXajowtK0yf0hW +EpMTT5HaiAHhVuxTm61DG7L2/5Fz6oTgbt3YJjENB5jDF1zNnq2x+wUMT41qHmQp95rX309X zhBZne+MGK1aIHvPn4m/snkuxUoE/atHZ7/dr2JEGg7f3zguW1VzS8b+FJDHBzf8LPxSQ1sQh yu0p+XKDQSZ9bVMlDC83UD8uGf0= Received-SPF: pass client-ip=212.227.15.19; envelope-from=deller@gmx.de; helo=mout.gmx.net X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_LOW=-0.7, 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 The qemu brk() implementation is too aggressive and cleans remaining bytes on the current page above the last brk address. But some existing applications are buggy and read/write bytes above their current heap address. On a phyiscal machine this does not trigger a runtime error as long as the access happens on the same page. Additionally the Linux kernel allocates only full pages and does no zeroing on already allocated pages, even if the brk address is lowered. Fix qemu to behave the same way as the kernel does. Do not touch already allocated pages, and - when running with different page sizes of guest and host - zero out only those memory areas where the host page size is bigger than the guest page size. Signed-off-by: Helge Deller Tested-by: "Markus F.X.J. Oberhumer" Fixes: 86f04735ac ("linux-user: Fix brk() to release pages") Cc: qemu-stable@nongnu.org Buglink: https://github.com/upx/upx/issues/683 --- linux-user/syscall.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) -- 2.41.0 diff --git a/linux-user/syscall.c b/linux-user/syscall.c index c99ef9c01e..ee54eed33b 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -829,10 +829,8 @@ abi_long do_brk(abi_ulong brk_val) /* brk_val and old target_brk might be on the same page */ if (new_brk == TARGET_PAGE_ALIGN(target_brk)) { - if (brk_val > target_brk) { - /* empty remaining bytes in (possibly larger) host page */ - memset(g2h_untagged(target_brk), 0, new_host_brk_page - target_brk); - } + /* empty remaining bytes in (possibly larger) host page */ + memset(g2h_untagged(new_brk), 0, new_host_brk_page - new_brk); target_brk = brk_val; return target_brk; } @@ -840,7 +838,7 @@ abi_long do_brk(abi_ulong brk_val) /* Release heap if necesary */ if (new_brk < target_brk) { /* empty remaining bytes in (possibly larger) host page */ - memset(g2h_untagged(brk_val), 0, new_host_brk_page - brk_val); + memset(g2h_untagged(new_brk), 0, new_host_brk_page - new_brk); /* free unused host pages and set new brk_page */ target_munmap(new_host_brk_page, brk_page - new_host_brk_page); @@ -873,7 +871,7 @@ abi_long do_brk(abi_ulong brk_val) * come from the remaining part of the previous page: it may * contains garbage data due to a previous heap usage (grown * then shrunken). */ - memset(g2h_untagged(target_brk), 0, brk_page - target_brk); + memset(g2h_untagged(brk_page), 0, HOST_PAGE_ALIGN(brk_page) - brk_page); target_brk = brk_val; brk_page = new_host_brk_page;