"Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com> writes:
> [ text/plain ] > Michael Ellerman <m...@ellerman.id.au> writes: > >> [ text/plain ] >> On Fri, 2016-18-03 at 04:01:21 UTC, Andrew Donnellan wrote: >>> When handling page faults, cxl_handle_page_fault() checks whether the page >>> should be accessible by userspace and have its _PAGE_USER access bit set. >>> _PAGE_USER should be set if the context's kernel flag isn't set, or if the >>> page falls outside of kernel memory. >>> >>> However, the check currently uses the wrong operator, causing it to always >>> evalute to true. As such, we always set the _PAGE_USER bit, even when it >>> should be restricted to the kernel. >>> >>> Fix the check so that the _PAGE_USER bit is set only as intended. >>> >> .. >>> diff --git a/drivers/misc/cxl/fault.c b/drivers/misc/cxl/fault.c >>> index 9a8650b..a76cb8a 100644 >>> --- a/drivers/misc/cxl/fault.c >>> +++ b/drivers/misc/cxl/fault.c >>> @@ -152,7 +152,7 @@ static void cxl_handle_page_fault(struct cxl_context >>> *ctx, >>> access = _PAGE_PRESENT; >>> if (dsisr & CXL_PSL_DSISR_An_S) >>> access |= _PAGE_RW; >>> - if ((!ctx->kernel) || ~(dar & (1ULL << 63))) >>> + if ((!ctx->kernel) || !(dar & (1ULL << 63))) >>> access |= _PAGE_USER; >> >> I think you can (should) use is_kernel_addr() for the DAR check. >> >> I'm also slightly worried by that logic in the case of a non-kernel context. >> >> ie. if ctx->kernel is false, we get: >> >> if (true || !is_kernel_addr(dar)) >> access |= _PAGE_USER; >> >> Which means we just add _PAGE_USER for any address. What am I missing here? > > I noticed this when doing radix support and have a variant posted at > > https://lists.ozlabs.org/pipermail/linuxppc-dev/2016-March/141036.html > My change also keep it similar to __hash_page. /* * We need to set the _PAGE_USER bit if MSR_PR is set or if we are * accessing a userspace segment (even from the kernel). We assume * kernel addresses always have the high bit set. */ if ((msr & MSR_PR) || (REGION_ID(ea) == USER_REGION_ID)) If we need this change to go in this merge window i can respin my patch. -aneesh _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
