From mboxrd@z Thu Jan 1 00:00:00 1970 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 6EAB047AF65 for ; Tue, 18 Aug 2026 17:57:52 +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=1787075873; cv=none; b=M0pYZTr8T5a9RqKZ0K91KEUIDAwXrYGQlqH2lKLLvhwARQy9ozB2l1DagvZINlpxao871zRLtedkaQHC9QUIZJNtrsilThoKtyGut5nIVgFqbWlRcznroRd6lQnQ2htoRNVrhSe3AqOkwJEL00n9i8BcSoGVcyUU7oObqHWhnyA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787075873; c=relaxed/simple; bh=HR7I/Rv+0Qgz8DlqLv6LWVlChV2EHKWycAqFjMyBqW0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=vF7jk7cpvfCeLShFcjUb0EW68J+vOaE/uz6JccdDRAeypMXdM8RbfQgMnPB0m29a/Sa5NMVq1CFXEiUOObZnYVVgOvoWVnehDPWDKkssaoHySdjv1HM1DJmUExRxUz9zluIYapMRqgGq862a8N+80F3deP3EigQvpPuTPH57+y8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aLAzgind; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="aLAzgind" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7798E1F00A3A; Tue, 18 Aug 2026 17:57:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787075872; bh=Ac/1VZjvsWRocdEDGsJDZs2a+ZC6CnTr9jKHO6X64Bg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=aLAzgindGjrnUKxCuyS2O/uGBDa7Zgy6zKk4iYIX0wY13iZPV1UqwQuKnytFzfksy e4q5JRJCaTpRcxwWh+ZV8dYImjZiltUmh+BuBQquWlUiLFNUTo71gLvzfhkhvezosZ 3pI9UDFBh7ov88TH62lWNf/AHE5u1tXwAiR0Q9vLKczBuS+pyU5BOJHHTYXSjRL2gi +OpqzPPfj6aocQkuKGYSW6kLKeTul1sydABBEaW2VY6OSwM2G/Cj6SJ1AlAiRpcb+e k+D66Wm4B5NmlC3UKM7VfQiOpV6Zucw8JBYzEBGDTUGnuPAoXz1sCeoJvosaJFYamq ahcaxe8ggurYw== From: Sasha Levin To: stable@vger.kernel.org Cc: Baul Lee , Federico Kirschbaum , Takashi Iwai , Sasha Levin Subject: [PATCH 5.10.y 2/2] ALSA: usx2y: bound the hwdep mmap fault offset Date: Tue, 18 Aug 2026 13:57:49 -0400 Message-ID: <20260818175749.2748626-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260818175749.2748626-1-sashal@kernel.org> References: <2026081720-deviant-snipping-e432@gregkh> <20260818175749.2748626-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Baul Lee [ Upstream commit 2ca1eea3cd17930daffe9e429a7c89232036ec24 ] snd_us428ctls_vm_fault() turns the faulting page offset into a kernel address with no bound of any kind: offset = vmf->pgoff << PAGE_SHIFT; vaddr = (char *)(...)->us428ctls_sharedmem + offset; page = virt_to_page(vaddr); get_page(page); vmf->page = page; return 0; snd_us428ctls_mmap() checks only the length of the mapping, never the offset, and us428ctls_sharedmem is a single page from alloc_pages_exact(). For a character device file_mmap_size_max() returns ULONG_MAX, so the mm layer imposes no ceiling either. Every page offset above zero resolves to a struct page outside the object, and the handler installs it into the caller's address space read-write; the vma is not marked read-only. The caller picks the page frame with a single mmap() argument and gets read-write access to a page of kernel memory it does not own; an offset that lands in an unpopulated vmemmap region oopses instead. A process that can open the hwdep node of an attached US-X2Y reaches this after loading the FPGA image through the same node; no capability check is involved. On 7.2.0-rc5 (arm64), mmap() with a large offset: Unable to handle kernel paging request at virtual address fffffdffc45d5ac8 pc : snd_us428ctls_vm_fault+0x68/0x140 [snd_usb_usx2y] Call trace: snd_us428ctls_vm_fault+0x68/0x140 [snd_usb_usx2y] __do_fault __handle_mm_fault handle_mm_fault el0_da Reject any offset outside the shared region. The pcm hwdep handler in usx2yhwdeppcm.c computes its address the same way and needs the same bound. Discovered by XBOW, triaged by Baul Lee Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Federico Kirschbaum Reported-by: Baul Lee Cc: stable@vger.kernel.org Signed-off-by: Baul Lee Link: https://patch.msgid.link/20260805013445.38283-1-baul.lee@xbow.com Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin --- sound/usb/usx2y/usX2Yhwdep.c | 2 ++ sound/usb/usx2y/usx2yhwdeppcm.c | 2 ++ 2 files changed, 4 insertions(+) diff --git a/sound/usb/usx2y/usX2Yhwdep.c b/sound/usb/usx2y/usX2Yhwdep.c index 0ed50be89271..eeafe580d038 100644 --- a/sound/usb/usx2y/usX2Yhwdep.c +++ b/sound/usb/usx2y/usX2Yhwdep.c @@ -29,6 +29,8 @@ static vm_fault_t snd_us428ctls_vm_fault(struct vm_fault *vmf) vmf->pgoff); offset = vmf->pgoff << PAGE_SHIFT; + if (offset >= US428_SHAREDMEM_PAGES) + return VM_FAULT_SIGBUS; vaddr = (char *)((struct usx2ydev *)vmf->vma->vm_private_data)->us428ctls_sharedmem + offset; page = virt_to_page(vaddr); get_page(page); diff --git a/sound/usb/usx2y/usx2yhwdeppcm.c b/sound/usb/usx2y/usx2yhwdeppcm.c index b988a4870de4..3f6e87f30f7e 100644 --- a/sound/usb/usx2y/usx2yhwdeppcm.c +++ b/sound/usb/usx2y/usx2yhwdeppcm.c @@ -674,6 +674,8 @@ static vm_fault_t snd_usx2y_hwdep_pcm_vm_fault(struct vm_fault *vmf) void *vaddr; offset = vmf->pgoff << PAGE_SHIFT; + if (offset >= USX2Y_HWDEP_PCM_PAGES) + return VM_FAULT_SIGBUS; vaddr = (char *)((struct usx2ydev *)vmf->vma->vm_private_data)->hwdep_pcm_shm + offset; vmf->page = virt_to_page(vaddr); get_page(vmf->page); -- 2.53.0