Hi Catalin,
On 6/10/2020 5:06 PM, Catalin Marinas wrote:
On Wed, Jun 10, 2020 at 04:39:44PM +0530, Shyam Thombre wrote:KASAN sw tagging sets a random tag of 8 bits in the top byte of the pointer returned by the memory allocating functions. So for the functions unaware of this change, the top 8 bits of the address must be reset which is done by the function arch_kasan_reset_tag(). Signed-off-by: Shyam Thombre <sthom...@codeaurora.org> --- arch/arm64/mm/mmu.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index e7fbc62..eae7655 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -723,6 +723,7 @@ int kern_addr_valid(unsigned long addr) pmd_t *pmdp, pmd; pte_t *ptep, pte;+ addr = arch_kasan_reset_tag(addr);if ((((long)addr) >> VA_BITS) != -1UL) return 0;It would be interesting to know what fails without this patch. The only user seems to be read_kcore() and, at a quick look, I don't see how it can generate tagged addresses.
This issue is seen in downstream GPU drivers. It currently doesn't look to impact any upstream users.
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