Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 495483DEFE2; Thu, 17 Sep 2026 17:12:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789665172; cv=none; b=E9zwDG+kYY5+6fSVGZHt1FuTcBODol1XBOa3+9C8yxvp1EgtExTfmqhAEyK9HHu0VtcmHD0GZWZf3Kv6lfafoJkCyvke0vMW9x/Taj/7Ir757iptjmdrDhbWnVtT2PSaRWEdrIy+ooyuDO0k0p9uV5GOWzoL5b+ta46SW338hV0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789665172; c=relaxed/simple; bh=no6lY7026nAqQuOXzn8AmbrC9OxqYz+fau+oVjtRKws=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Tyz8AwUOj08UYlu3duYvlbJm9eeX/bIrlT2bMGw1lFTMykgM5yaB3iHAQQyQ+aOed/E+OWYJwPpl++lODaSCm70Lcber9zawBraElLejLHgD0fknPJGwrJ/w3bdm1XkycXq8hrNLc4gwSlVsEgpmfm2jmyitZKWx4p/8KaHv4xw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=09iQH0Re; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="09iQH0Re" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 952F91F000FF; Thu, 17 Sep 2026 17:12:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789665171; bh=uKJdXksY4/7rQUAHhGkDlntzpyBcQ8jTYRfawLY6Ed0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=09iQH0Re7JCMf6ZFwROtlKJU2WjQ1fOuShtbr1QePaQhlv553TBs4iv8kWWsT8LHq nefbrg/f/iGiuVoZSuTL1SH9kXBERt+yYTQehNtbka9DGS3nxTWh31WWABW5RSbNOL LlKxwr9f85qtD+WgJ4+kRq56zz2xqbpgB0sGdat4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+2442951a6abb004df963@syzkaller.appspotmail.com, Slawomir Stepien , Thomas Zimmermann , Sasha Levin Subject: [PATCH 6.18 0617/1250] drm/cirrus-qemu: Validate BAR0 size during probe Date: Thu, 17 Sep 2026 16:06:52 +0100 Message-ID: <20260917151608.594155483@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151551.901433442@linuxfoundation.org> References: <20260917151551.901433442@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Slawomir Stepien [ Upstream commit 92312d333bf700798f92f30406c721bce87506f3 ] The `cirrus-qemu` driver relies on `CIRRUS_VRAM_SIZE` (4 MB) to validate framebuffer sizes. However, during PCI probe, the driver mapped BAR0 without verifying that its size matches `CIRRUS_VRAM_SIZE`. If a PCI device with a BAR0 smaller than 4 MB is bound to the driver, the mapped VRAM will be smaller than expected. Because validation checks assume 4 MB VRAM, framebuffers larger than the mapped memory can be created. When the display plane is updated (e.g. during release), `cirrus_primary_plane_helper_atomic_update()` copies the framebuffer to VRAM using `drm_fb_memcpy()`. Writing past the end of the mapped I/O memory causes a supervisor write page fault: BUG: unable to handle page fault for address: ffffc9000389c000 ... RIP: 0010:memcpy_toio+0x7c/0xe0 arch/x86/lib/iomem.c:110 ... Call Trace: iosys_map_memcpy_to include/linux/iosys-map.h:285 [inline] drm_fb_memcpy+0x325/0x5d0 drivers/gpu/drm/drm_format_helper.c:442 cirrus_primary_plane_helper_atomic_update+0x98a/0xb00 drivers/gpu/drm/tiny/cirrus-qemu.c:358 drm_atomic_helper_commit_planes+0x626/0xea0 drivers/gpu/drm/drm_atomic_helper.c:3038 drm_atomic_helper_commit_tail+0x60/0x510 drivers/gpu/drm/drm_atomic_helper.c:1989 commit_tail+0x2b1/0x3c0 drivers/gpu/drm/drm_atomic_helper.c:2074 drm_atomic_helper_commit+0xa77/0xb10 drivers/gpu/drm/drm_atomic_helper.c:2312 Fix this by validating in `cirrus_pci_probe()` that the PCI BAR0 resource is not less than `CIRRUS_VRAM_SIZE`, returning `-ENODEV` if it is less. Fixes: ab3e023b1b4c ("drm/cirrus: rewrite and modernize driver.") Assisted-by: Gemini:gemini-3.6-flash Gemini:gemini-3.1-pro-preview syzbot Reported-by: syzbot+2442951a6abb004df963@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2442951a6abb004df963 Link: https://syzkaller.appspot.com/ai_job?id=ba262a3a-bccf-4ad8-a1b0-583c55d34fd6 Signed-off-by: Slawomir Stepien Signed-off-by: Thomas Zimmermann Reviewed-by: Thomas Zimmermann Link: https://patch.msgid.link/20260825120729.493611-1-sst@poczta.fm Signed-off-by: Sasha Levin --- drivers/gpu/drm/tiny/cirrus-qemu.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/gpu/drm/tiny/cirrus-qemu.c b/drivers/gpu/drm/tiny/cirrus-qemu.c index 97a93adc5669d..a6ce6aa99477e 100644 --- a/drivers/gpu/drm/tiny/cirrus-qemu.c +++ b/drivers/gpu/drm/tiny/cirrus-qemu.c @@ -570,6 +570,9 @@ static int cirrus_pci_probe(struct pci_dev *pdev, struct cirrus_device *cirrus; int ret; + if (pci_resource_len(pdev, 0) < CIRRUS_VRAM_SIZE) + return -ENODEV; + ret = aperture_remove_conflicting_pci_devices(pdev, cirrus_driver.name); if (ret) return ret; -- 2.53.0