From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792424132; b=UwPd6Y/JxKrRDeC83DSsMiA544t+ZVOLnJEgPNNN43slZbubjS4FOnO5MxG4TqjsbWvE nENFIfEMgc85Cb4hg8G60OfcZ1fZt54JRztpiaJRxpPLrqLjkVG1jooBdHII1uFjpbcUg lvm/2Nh+9HOIW/wmfF/w1qa7y/RMoV3tZDndxD//2yi+FSeu2JL4xNgM73uu+0Vv4mIe2 2dOuve6uBAeecyh/8twQGBt/MtOrQZR+K7Fh9doVtwz3HER4G9Zqh/IMPtzGfRhhndkxR olXNi/KbQ1wACFkYuO6Tlxlg8VB2XPZ/X1zsfxUh1ITZ+aaXrGupziOJQwbLUylvCdQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792424132; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-Id: In-Reply-To:References:X-Mailer:Mime-Version:Content-Type: Content-Transfer-Encoding; bh=pctsoJTIi3PIcREBl4WC4IIZ1RXf5gRECxbUB6cpZoM=; b=ukk7t8iIeByximaYe2RGfxPe+zRDuQJDcb6JVbMQSBf31hnu7j/wmOSZ50WkyO5iORSd g+7inWcyKwQSF5qY2mgwsGbAnr1m49cqGwovp+2X+dq62zKzpxbtMVN3P9hf3Yt6wfbN3 Pqnll/rl+GiQzsI5Fb/mCO4UhhLCPITTKOW12x2FHSk3F0OV0nKagT9QKByYEgEdh0sxW RWsswouqfHJExoyw/f6Qhfo81SG+O67QzFpOPht+RM7BpJuK5uUtWKHfKh1TNd+QLRPo8 0xGi3GftsqYTa7/jlEslJWMvNaijlcfP32fWzDLWnswe3qZVUJYJfRDicXj4BtmaoTg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=YYbUVaVN; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 383586072499 for ; Mon, 19 Oct 2026 15:35:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=YYbUVaVN Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C5701F0283C; Mon, 19 Oct 2026 15:35:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1792424130; bh=pctsoJTIi3PIcREBl4WC4IIZ1RXf5gRECxbUB6cpZoM=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=YYbUVaVNFOS3ikdPPAI0feyllwwC0JAn5J9+vzlGaHw385Cbra4uKCOAehI4fLL8d lHqVkJr9iabcTmrdzSgeBqF6ufaO1VZQSw1fIO7wQjJxWubhEDsZZl+opqfQn0DQtO x5+6ZpH9ghkNIilJ1vs0fiqHzhnyP3e7b78PTCkQ= Date: Mon, 19 Oct 2026 08:35:29 -0700 From: Andrew Morton To: Nikola Ciprich Cc: Sean Christopherson , Borislav Petkov , David Laight , Rik van Riel , ljs@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, david@kernel.org, Mike Rapoport , Dave Hansen , Pedro Falcato , Kiryl Shutsemau , luizcap@redhat.com, pbonzini@redhat.com, Tal Zussman , Matt Fleming , Yosry Ahmed Subject: Re: hunting memory corruption bug in 6.18.x Message-Id: <20261019083529.a81910ac0976c1a5687d4c6a@linux-foundation.org> In-Reply-To: References: <20261014235736.GCatAW8GD0GlYumL4l@fat_crate.local> <20261015172820.7961d2c0def74d41cc6c4b0c@linux-foundation.org> <20261016031242.GDatGWKo98YSOhEOOn@fat_crate.local> <20261015211832.45d87fab15bb3e0bbc2f47cb@linux-foundation.org> <20261016054954.GEatG7AgMNFRkiTo1H@fat_crate.local> <20261018201538.d0957878f378a9821852836f@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Mon, 19 Oct 2026 17:22:37 +0200 Nikola Ciprich wrote: > > > > Sure! And I have more good news: after applying 55780d8a1dcc > > to 6.18.56, I was able to perform more than 30 migrations without > > a glitch. After booting back into 6.18.56 without it, both VMs > > crashed within 2-3 migrations. Furthermore, some memory apparently > > got corrupted on one of the hosts, since various commands started > > crashing too: > > > > [ 303.466091] traps: systemd-logind[3085] trap invalid opcode ip:7f7b5667e616 sp:7ffe1afdec38 error:0 in libsystemd-shared-252.so[7e616,7f7b5666d000+22e000] > > [ 303.493810] traps: systemd-coredum[11269] trap invalid opcode ip:7fc6bf67f614 sp:7ffc075da958 error:0 in libsystemd-shared-252.so[7f614,7fc6bf66d000+22e000] > > [ 377.528955] traps: systemd[5607] trap invalid opcode ip:7f791447e616 sp:7ffe83e61cf8 error:0 in libsystemd-shared-252.so[7e616,7f791446d000+22e000] > > [ 377.556993] traps: systemd-coredum[12080] trap invalid opcode ip:7f97ce07f614 sp:7ffe28b56a88 error:0 in libsystemd-shared-252.so[7f614,7f97ce06d000+22e000] > > [ 3746.173043] traps: hostnamectl[45846] trap invalid opcode ip:7fe00cc7f614 sp:7fff89916e48 error:0 in libsystemd-shared-252.so[7f614,7fe00cc6d000+22e000] > > [ 3746.202305] traps: systemd-coredum[45847] trap invalid opcode ip:7f7fe9e7f614 sp:7ffea227cfa8 error:0 in libsystemd-shared-252.so[7f614,7f7fe9e6d000+22e000] > > [ 3750.581940] traps: systemctl[45903] trap invalid opcode ip:7fbb8967f614 sp:7fff733e5748 error:0 in libsystemd-shared-252.so[7f614,7fbb8966d000+22e000] > > [ 3750.612651] traps: systemd-coredum[45904] trap invalid opcode ip:7f90d347f614 sp:7ffdc7f55148 error:0 in libsystemd-shared-252.so[7f614,7f90d346d000+22e000] > > > > I'm not sure if this is of any use, but I collected a vmcore of > > this state by intentionally crashing the host via /proc/sysrq-trigger. > > > > Anyway, I'll give 55780d8a1dcc some more migration rounds, but it looks > > promising. > > 500+ migrations back and forth, no issues. I consider this solved and am rolling > out the patched kernel; I’ll report if anything new turns up. Great, thanks. oops, we haven't been cc'ing Yosry. > Definitely a -stable candidate. Andrew, will you send it to Greg, or shall I? I volunteer Yosry or Sean ;) I think 55780d8a1dcc should be repackaged before sending over to the -stable people. Its changelog is very wrong: "The bug is benign though". Update the changelog to explain that the bug is in fact evil. Otherwise -stable and further downstream won't understand why we sent it to them and won't understand the impact. And that repackaging would be an opportunity to add Reported-by:/Closes:/Tested-by: you, which is the least we can do to thank you for all this diligent work!