linux-kernel - Re: [syzbot] [iommu?] kernel BUG in dma_alloc

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Message-ID: <20241016080240.GA30380@lst.de>
Date: Wed, 16 Oct 2024 10:02:40 +0200
From: Christoph Hellwig <hch@....de>
To: syzbot <syzbot+b4bfacdec173efaa8567@...kaller.appspotmail.com>
Cc: hch@....de, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
	m.szyprowski@...sung.com, robin.murphy@....com,
	syzkaller-bugs@...glegroups.com,
	Sean Anderson <sean.anderson@...ux.dev>
Subject: Re: [syzbot] [iommu?] kernel BUG in dma_alloc_attrs

The problem is that the dma alloc/free tracing calls virt_to_phys
on the allocated/free memory.  But that memory can be vmalloced as
in this case.  I think we don't have weirdo allocators or pools any
more that are neither in the direct kernel mapping or vmalloc, so
we might be able to do an

		if (is_vmalloc_addr())
			page_to_phys(vmalloc_to_page()))
		else
			virt_to_page()

here.  Or just switch to tracing the virtual address to always be
on the safe side.