From nobody Sat Feb 7 12:05:55 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 582E648CFE; Mon, 5 Feb 2024 19:01:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707159699; cv=none; b=CYkotU4VhUsCGFsEW/zABKhkgGfUMXlVoI64HYywpCMF5L4lw4HFLej6WudTs+wORuijmPKeq+n2v6ws4gw7RlEvzWdVtbcyRcMB+wIhsNdE7xdP33/rbuvah70xlbf/brshj5Ad9Xtd3acvIdkU+/VRE0OEgqSJjJcC+ZeWMCw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707159699; c=relaxed/simple; bh=q1DctEBmJoDY/umidsjcFfwC11ROonZMe8mf1M+EGs0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ucKUDpSybKyNGZoM6nMGO4a87yY7QEYJ5bvvBxMKNvdy9pMqBsGSGc3SRRjtiwIChmncXvmTlfLMuRJmEjfLKXBFX+s3nAxZkV/g5Oo0UqkoXqRK1fcTkUoUiVm/Ooqa23Rhd+jZhjU1Mu5ZuDfZjwyOby37rv8p8e6zrTsUcRk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lKWhAX/r; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lKWhAX/r" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 123FCC433F1; Mon, 5 Feb 2024 19:01:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1707159698; bh=q1DctEBmJoDY/umidsjcFfwC11ROonZMe8mf1M+EGs0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lKWhAX/r0SSww5PSxbVGrO4q2dskM4sK4uZZ20Cpo4oNq83EEsVORFqLLBcsvg2PP HKkKJovaEtF1aHtMHpBu2M5FPMx0c1sJxQb1gA+XcsTU4pf4fhFDl62zvf64zjJtQ/ ita18vLaf9lcnMzi5tCBJwA9imsVMITnGmHMtiEbthic8DgGcxJtodc0TAkAjYtrgN GjJo8Y6kvNlhwGNlEh5TN4qVIYDBhazuusrfnLULMhYABHT19ga+W6U2ixDywLJ14W RSRt65VyZSRcDSb4GyYeQLWsskDlQUsx2CRsESpH2uRT6BzhL9bDRz+4dOVsSrxaGX 8W5Z7Wqdx/uCg== From: Will Deacon To: linux-kernel@vger.kernel.org Cc: kernel-team@android.com, Will Deacon , iommu@lists.linux.dev, Christoph Hellwig , Marek Szyprowski , Robin Murphy , Petr Tesarik , Dexuan Cui Subject: [PATCH v3 1/3] swiotlb: Fix double-allocation of slots due to broken alignment handling Date: Mon, 5 Feb 2024 19:01:25 +0000 Message-Id: <20240205190127.20685-2-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20240205190127.20685-1-will@kernel.org> References: <20240205190127.20685-1-will@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Commit bbb73a103fbb ("swiotlb: fix a braino in the alignment check fix"), which was a fix for commit 0eee5ae10256 ("swiotlb: fix slot alignment checks"), causes a functional regression with vsock in a virtual machine using bouncing via a restricted DMA SWIOTLB pool. When virtio allocates the virtqueues for the vsock device using dma_alloc_coherent(), the SWIOTLB search can return page-unaligned allocations if 'area->index' was left unaligned by a previous allocation from the buffer: # Final address in brackets is the SWIOTLB address returned to the caller | virtio-pci 0000:00:07.0: orig_addr 0x0 alloc_size 0x2000, iotlb_align_ma= sk 0x800 stride 0x2: got slot 1645-1649/7168 (0x98326800) | virtio-pci 0000:00:07.0: orig_addr 0x0 alloc_size 0x2000, iotlb_align_ma= sk 0x800 stride 0x2: got slot 1649-1653/7168 (0x98328800) | virtio-pci 0000:00:07.0: orig_addr 0x0 alloc_size 0x2000, iotlb_align_ma= sk 0x800 stride 0x2: got slot 1653-1657/7168 (0x9832a800) This ends badly (typically buffer corruption and/or a hang) because swiotlb_alloc() is expecting a page-aligned allocation and so blindly returns a pointer to the 'struct page' corresponding to the allocation, therefore double-allocating the first half (2KiB slot) of the 4KiB page. Fix the problem by treating the allocation alignment separately to any additional alignment requirements from the device, using the maximum of the two as the stride to search the buffer slots and taking care to ensure a minimum of page-alignment for buffers larger than a page. Fixes: bbb73a103fbb ("swiotlb: fix a braino in the alignment check fix") Fixes: 0eee5ae10256 ("swiotlb: fix slot alignment checks") Cc: Christoph Hellwig Cc: Marek Szyprowski Cc: Robin Murphy Cc: Petr Tesarik Cc: Dexuan Cui Signed-off-by: Will Deacon Reviewed-by: Petr Tesarik --- kernel/dma/swiotlb.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-) diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index b079a9a8e087..9ff909a0039a 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -982,7 +982,7 @@ static int swiotlb_search_pool_area(struct device *dev,= struct io_tlb_pool *pool phys_to_dma_unencrypted(dev, pool->start) & boundary_mask; unsigned long max_slots =3D get_max_slots(boundary_mask); unsigned int iotlb_align_mask =3D - dma_get_min_align_mask(dev) | alloc_align_mask; + dma_get_min_align_mask(dev) & ~(IO_TLB_SIZE - 1); unsigned int nslots =3D nr_slots(alloc_size), stride; unsigned int offset =3D swiotlb_align_offset(dev, orig_addr); unsigned int index, slots_checked, count =3D 0, i; @@ -993,19 +993,18 @@ static int swiotlb_search_pool_area(struct device *de= v, struct io_tlb_pool *pool BUG_ON(!nslots); BUG_ON(area_index >=3D pool->nareas); =20 + /* + * For mappings with an alignment requirement don't bother looping to + * unaligned slots once we found an aligned one. + */ + stride =3D get_max_slots(max(alloc_align_mask, iotlb_align_mask)); + /* * For allocations of PAGE_SIZE or larger only look for page aligned * allocations. */ if (alloc_size >=3D PAGE_SIZE) - iotlb_align_mask |=3D ~PAGE_MASK; - iotlb_align_mask &=3D ~(IO_TLB_SIZE - 1); - - /* - * For mappings with an alignment requirement don't bother looping to - * unaligned slots once we found an aligned one. - */ - stride =3D (iotlb_align_mask >> IO_TLB_SHIFT) + 1; + stride =3D max(stride, PAGE_SHIFT - IO_TLB_SHIFT + 1); =20 spin_lock_irqsave(&area->lock, flags); if (unlikely(nslots > pool->area_nslabs - area->used)) @@ -1015,11 +1014,14 @@ static int swiotlb_search_pool_area(struct device *= dev, struct io_tlb_pool *pool index =3D area->index; =20 for (slots_checked =3D 0; slots_checked < pool->area_nslabs; ) { - slot_index =3D slot_base + index; + phys_addr_t tlb_addr; =20 - if (orig_addr && - (slot_addr(tbl_dma_addr, slot_index) & - iotlb_align_mask) !=3D (orig_addr & iotlb_align_mask)) { + slot_index =3D slot_base + index; + tlb_addr =3D slot_addr(tbl_dma_addr, slot_index); + + if ((tlb_addr & alloc_align_mask) || + (orig_addr && (tlb_addr & iotlb_align_mask) !=3D + (orig_addr & iotlb_align_mask))) { index =3D wrap_area_index(pool, index + 1); slots_checked++; continue; --=20 2.43.0.594.gd9cf4e227d-goog From nobody Sat Feb 7 12:05:55 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A3B074BA96; Mon, 5 Feb 2024 19:01:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; 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Mon, 5 Feb 2024 19:01:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1707159701; bh=Xm+zNHaI1L6yDroz8J/2SUT0P9yQzO240Q33Rj/NF8c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GkLGdqbtVBK2Cn0h+xSZ/PXnBH9ZzuzbPxDZyJevoa4KTz2c2JKWo1J2L05OMfoS4 yE2WSQWMmIr+86D8xLTHJrok/gyrBAGAuVSDbJfev3T4Mcxq4ey++Ii6xYQfBWJgJ7 ppbmSp9LecvqGB8aOHD4Iz2LQZOpnoPbcFjjgh6dZfFO0sOan7u5OnFvMFCnrgLcKj L20sMxRTnQakMyFSO7MkjdfUERnK3w63JicuVJcWO3zHLWTmH1pK4/uc6K2KZJGaLJ 7XHeeFFe0RO8KFvhdwCa3HHZWuL8rJMcM8DBSsgLZqmZ4dYC9A5VTsYUJzHrJfd78Y x7YJ6seoe6whw== From: Will Deacon To: linux-kernel@vger.kernel.org Cc: kernel-team@android.com, Will Deacon , iommu@lists.linux.dev, Christoph Hellwig , Marek Szyprowski , Robin Murphy , Petr Tesarik , Dexuan Cui Subject: [PATCH v3 2/3] swiotlb: Enforce page alignment in swiotlb_alloc() Date: Mon, 5 Feb 2024 19:01:26 +0000 Message-Id: <20240205190127.20685-3-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20240205190127.20685-1-will@kernel.org> References: <20240205190127.20685-1-will@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When allocating pages from a restricted DMA pool in swiotlb_alloc(), the buffer address is blindly converted to a 'struct page *' that is returned to the caller. In the unlikely event of an allocation bug, page-unaligned addresses are not detected and slots can silently be double-allocated. Add a simple check of the buffer alignment in swiotlb_alloc() to make debugging a little easier if something has gone wonky. Cc: Christoph Hellwig Cc: Marek Szyprowski Cc: Robin Murphy Cc: Petr Tesarik Cc: Dexuan Cui Signed-off-by: Will Deacon Reviewed-by: Petr Tesarik --- kernel/dma/swiotlb.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 9ff909a0039a..adbb3143238b 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -1643,6 +1643,12 @@ struct page *swiotlb_alloc(struct device *dev, size_= t size) return NULL; =20 tlb_addr =3D slot_addr(pool->start, index); + if (unlikely(!PAGE_ALIGNED(tlb_addr))) { + dev_WARN_ONCE(dev, 1, "Cannot allocate pages from non page-aligned swiot= lb addr 0x%pa.\n", + &tlb_addr); + swiotlb_release_slots(dev, tlb_addr); + return NULL; + } =20 return pfn_to_page(PFN_DOWN(tlb_addr)); } --=20 2.43.0.594.gd9cf4e227d-goog From nobody Sat Feb 7 12:05:55 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 BFE5B4D5A2; Mon, 5 Feb 2024 19:01:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707159703; cv=none; b=TEStmv/W4HEh2xs4ZnHa0gMW9L6OKfT5dd/ZnZrdYylJca7xzWOugSZFR1MzqAbnkTqyYOGJ9E9jhPdnrI/X9Wx8jActuSQ2WMcASEbf9Jp82yoz/FOn4CinjUhVinFdQj6fDaF+NAf1DQmDhhp88/PAZIDesDPc49zS/53SdWY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707159703; c=relaxed/simple; bh=hQZUe3sC6qvAlN4FEOPtkqPiMEdJZuABY+olfP99JFc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=onhezXw0PNdLALIc2dmdLq9lhso9r6kdxNd6q45rbosFwGI5wClEpu6DyIYCXyLYeHlNgIEALwSMeglPE1Lpp+DZSzj/6BUvHlO70B0CHDp2BIEt5eqZVNHmSaYNde6pyt+JTG6CTTcmjGA53lKajO3xserM8g9Q2ztUSz4mrA0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lmoQR25l; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lmoQR25l" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FB3AC433F1; Mon, 5 Feb 2024 19:01:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1707159703; bh=hQZUe3sC6qvAlN4FEOPtkqPiMEdJZuABY+olfP99JFc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lmoQR25ludhgwq7pg6I1EhIk/p8uQEqt8nLNz7TzzLBOX2wlnQlMhVmrCVOaVrDmI oGP61dg+FoZ3JflOYRYPQgaDLxt6gMLeGUImiWBiwoQi3A+DFrUxQWBbvpgteIh7Nf RoNzLKYE075wvJp57XGu+9niQCouMmcWRsD/PyMTjOekbdS4ajwjOj4Y8yNQFANaT6 caBhmNO0eWy25b0h8FlrrDvpIze5J1cKCt2I8dfPMPV0j0PkszJ/02+LMdXZgYQQWn BUra+IidX2GQ5qUJH3X0XnOHipUoBWgrjTEas1zkICOsnv7QJwUUWmJ53edEGpT7qN FI3PM05JbV7fA== From: Will Deacon To: linux-kernel@vger.kernel.org Cc: kernel-team@android.com, Will Deacon , iommu@lists.linux.dev, Christoph Hellwig , Marek Szyprowski , Robin Murphy , Petr Tesarik , Dexuan Cui Subject: [PATCH v3 3/3] swiotlb: Honour dma_alloc_coherent() alignment in swiotlb_alloc() Date: Mon, 5 Feb 2024 19:01:27 +0000 Message-Id: <20240205190127.20685-4-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20240205190127.20685-1-will@kernel.org> References: <20240205190127.20685-1-will@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" core-api/dma-api-howto.rst states the following properties of dma_alloc_coherent(): | The CPU virtual address and the DMA address are both guaranteed to | be aligned to the smallest PAGE_SIZE order which is greater than or | equal to the requested size. However, swiotlb_alloc() passes zero for the 'alloc_align_mask' parameter of swiotlb_find_slots() and so this property is not upheld. Instead, allocations larger than a page are aligned to PAGE_SIZE, Calculate the mask corresponding to the page order suitable for holding the allocation and pass that to swiotlb_find_slots(). Cc: Christoph Hellwig Cc: Marek Szyprowski Cc: Robin Murphy Cc: Petr Tesarik Cc: Dexuan Cui Fixes: e81e99bacc9f ("swiotlb: Support aligned swiotlb buffers") Signed-off-by: Will Deacon Reviewed-by: Petr Tesarik --- kernel/dma/swiotlb.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index adbb3143238b..283eea33dd22 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -1633,12 +1633,14 @@ struct page *swiotlb_alloc(struct device *dev, size= _t size) struct io_tlb_mem *mem =3D dev->dma_io_tlb_mem; struct io_tlb_pool *pool; phys_addr_t tlb_addr; + unsigned int align; int index; =20 if (!mem) return NULL; =20 - index =3D swiotlb_find_slots(dev, 0, size, 0, &pool); + align =3D (1 << (get_order(size) + PAGE_SHIFT)) - 1; + index =3D swiotlb_find_slots(dev, 0, size, align, &pool); if (index =3D=3D -1) return NULL; =20 --=20 2.43.0.594.gd9cf4e227d-goog