Messages in this thread | | | Subject | Re: [patch 05/16] mm: Allow special mappings with user access cleared | From | Dave Hansen <> | Date | Wed, 13 Dec 2017 07:14:41 -0800 |
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On 12/13/2017 04:57 AM, Kirill A. Shutemov wrote: > Dave, what is effect of this on protection keys?
The goal was to make pkeys-protected userspace memory access _consistent_ with normal access. Specifically, we want a kernel to disallow access (or writes) to memory where userspace mapping has a pkey whose permissions are in conflict with the access.
For instance:
This will fault writing a byte to 'addr':
char *addr = malloc(PAGE_SIZE); pkey_mprotect(addr, PAGE_SIZE, 13); pkey_deny_access(13); *addr[0] = 'f';
But this will write one byte to addr successfully (if it uses the kernel mapping of the physical page backing 'addr'):
char *addr = malloc(PAGE_SIZE); pkey_mprotect(addr, PAGE_SIZE, 13); pkey_deny_access(13); read(fd, addr, 1);
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