From: Christoph Hellwig <hch@infradead.org>
To: Andrei-Edward Popa <andrei.popa105@yahoo.com>
Cc: m.szyprowski@samsung.com, robin.murphy@arm.com,
iommu@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dma-remap: fix dma_common_find_pages() page lookup for offsets
Date: Sun, 14 Dec 2025 21:57:59 -0800 [thread overview]
Message-ID: <aT-jZyXGTVz-ziff@infradead.org> (raw)
In-Reply-To: <20251212200914.138310-1-andrei.popa105@yahoo.com>
On Fri, Dec 12, 2025 at 10:09:14PM +0200, Andrei-Edward Popa wrote:
> dma_common_find_pages() previously assumed that the CPU virtual address
> always pointed to the start of a DMA-coherent allocation. This fails when
> memory is allocated via dma_alloc_attrs() without DMA_ATTR_FORCE_CONTIGUOUS
> and then subdivided into smaller blocks using a gen_pool, relevant only
> when an IOMMU is enabled.
>
> In such cases, userspace may request a mapping via dma_mmap_attrs()
> for a CPU address that is offset inside the original allocation. The
> previous code could return the wrong struct page pointer.
No, you can't mmap part of a dma coherent allocation. What caller is
trying to do this? It needs to be fixed instead.
next prev parent reply other threads:[~2025-12-15 5:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20251212200914.138310-1-andrei.popa105.ref@yahoo.com>
2025-12-12 20:09 ` Andrei-Edward Popa
2025-12-15 5:57 ` Christoph Hellwig [this message]
2025-12-15 8:13 ` Marek Szyprowski
2025-12-15 11:31 ` Robin Murphy
2025-12-15 20:49 ` Andrei-Edward Popa
2025-12-15 10:52 ` Robin Murphy
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