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Thu, 20 Aug 2026 13:19:49 +0000 (GMT) Received: from p1lg14885.dc01.its.hpecorp.net (unknown [10.119.18.236]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by p1lg14880.it.hpe.com (Postfix) with ESMTPS id 7382A8001B8; Thu, 20 Aug 2026 13:19:39 +0000 (UTC) Received: from hpe.com (unknown [16.231.227.39]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (Client did not present a certificate) by p1lg14885.dc01.its.hpecorp.net (Postfix) with ESMTPS id 593EA8036B8; Thu, 20 Aug 2026 13:19:39 +0000 (UTC) Date: Thu, 20 Aug 2026 08:19:37 -0500 From: Dimitri Sivanich To: Abdifatah Suruur Cc: linux-kernel@vger.kernel.org, Dimitri Sivanich Subject: Re: [PATCH] char: uv_mmtimer: prevent read-only mmtimer mapping from becoming writable Message-ID: References: <20260819084224.1594-1-suruurism@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260819084224.1594-1-suruurism@gmail.com> X-Proofpoint-GUID: 680ji_u7Y0YYgky3Fa1_pC9IcshtdJkQ X-Authority-Analysis: v=2.4 cv=YK2vDxGx c=1 sm=1 tr=0 ts=6a86fef5 cx=c_pps a=A+SOMQ4XYIH4HgQ50p3F5Q==:117 a=A+SOMQ4XYIH4HgQ50p3F5Q==:17 a=kj9zAlcOel0A:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=gQcMVamqm3wCPoSYhaRC:22 a=_ZmgHqWwjZUDpi_pur5s:22 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=MvuuwTCpAAAA:8 a=HPReF5U54dxshTXP3loA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: 680ji_u7Y0YYgky3Fa1_pC9IcshtdJkQ X-Proofpoint-Spam-Info: AW1haW4tMjYwODIwMDA5OSBTYWx0ZWRfXxXL71MAlXHSL Daxdej9qb+SVI6j91A5+j8Uh9jWRnKAQv4c6+j6WOlhJ/mIzYLIhVX4lJo9Mh2tdcR5HDaO2xAo 56Qc5GSDtEjuOBnEvGxW2SigVcVDHnY= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIwMDA5OSBTYWx0ZWRfX0dNHeplEp92k SjRWXEoT+O8kqdNZRjyxfk/YytrkQmDvQ+5z5eqC0jJ2tMOOCAvgZj6wwpC/gdmzZO+2Y7eHyX3 qXpXJAHPELxQ0t0avarN1k1+oAucdPV9GMWIzzSQK2sLATc8aK8rWrRnyrEJfC1cd0ibBqJqANQ qRUrCo5MWfcHQkyZIf2U0hzX/5SFAWj3IavcqVjQ2xrT09FSDSvUNN6VqiK38MTIL8RzkbJ8Whm ucMd67h9QJhXHCRaJNozJ9NJxqqVm20Wv78Z9nGrVpB0jQjconPvYnrUC6mM7tfsjHczSSiU0rR +cn/IU41trsilQNDe/Z/87/Xl+nauC5aGRd5s7d08lfwgkiCgU1uG62Hcn/OEK3y1Rtk/ilsGX0 hGqqACXicE4a0LpT2xCov9irxiHIZFTCGBzIBMjTlNpgJ0Aabv+U7LZaecdc1qSWRbROyu+DiK4 unhGeayt2Tyqmj23HnA== X-HPE-SCL: -1 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-19_06,2026-08-19_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 lowpriorityscore=0 impostorscore=0 suspectscore=0 clxscore=1011 adultscore=0 priorityscore=1501 bulkscore=0 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608200099 On Wed, Aug 19, 2026 at 11:42:24AM +0300, Abdifatah Suruur wrote: > uv_mmtimer_mmap() rejects writable mappings of the system-wide mmtimer > register page, but leaves VM_MAYWRITE set. Userspace can map the page > read-only and then upgrade the mapping to writable with mprotect(), > after which it can write to the shared RTC registers. > > Clear VM_MAYWRITE on the read-only path, as i915 does for its read-only > objects and as fixed in drm/vc4 (CVE-2026-68445) and drm/panthor > (CVE-2024-53071) and ptp: vmclock (commit > a5edadbae57e2298a56cf7a4e774a027905a331f). > > Fixes: fbd8ae106850b ("char: add SGI UV mmtimer driver") > Cc: stable@vger.kernel.org > Signed-off-by: Abdifatah Suruur > Acked-by: Dimitri Sivanich