From: Roland Dreier Date: Mon, 15 Sep 2008 10:43:35 +0000 (+0000) Subject: powerpc: Avoid integer overflow in page_is_ram() X-Git-Tag: v2.6.28-rc1~569^2~44 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a880e7623397bcb44877b012cd65baa11ad1bbf8;p=pandora-kernel.git powerpc: Avoid integer overflow in page_is_ram() Commit 8b150478 ("ppc: make phys_mem_access_prot() work with pfns instead of addresses") fixed page_is_ram() in arch/ppc to avoid overflow for addresses above 4G on 32-bit kernels. However arch/powerpc's page_is_ram() is missing the same fix -- it computes a physical address by doing pfn << PAGE_SHIFT, which overflows if pfn corresponds to a page above 4G. In particular this causes pages above 4G to be mapped with the wrong caching attribute; for example many ppc440-based SoCs have PCI space above 4G, and mmap()ing MMIO space may end up with a mapping that has caching enabled. Fix this by working with the pfn and avoiding the conversion to physical address that causes the overflow. This patch compares the pfn to max_pfn, which is a semantic change from the old code -- that code compared the physical address to high_memory, which corresponds to max_low_pfn. However, I think that was is another bug, since highmem pages are still RAM. Reported-by: vb Signed-off-by: Roland Dreier Acked-by: Benjamin Herrenschmidt Signed-off-by: Benjamin Herrenschmidt --- Reading git-diff-tree failed