Jan reported that LTP mmap03 was getting stuck in a page fault loop
after commit c46241a370 ("powerpc/pkeys: Check vma before returning
key fault error to the user"), as well as a minimised reproducer:
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
int main(int ac, char **av)
{
int page_sz = getpagesize();
int fildes;
char *addr;
fildes = open("tempfile", O_WRONLY | O_CREAT, 0666);
write(fildes, &fildes, sizeof(fildes));
close(fildes);
fildes = open("tempfile", O_RDONLY);
unlink("tempfile");
addr = mmap(0, page_sz, PROT_EXEC, MAP_FILE | MAP_PRIVATE, fildes, 0);
printf("%d\n", *addr);
return 0;
}
And noticed that access_pkey_error() in page fault handler now always
seem to return false:
__do_page_fault
access_pkey_error(is_pkey: 1, is_exec: 0, is_write: 0)
arch_vma_access_permitted
pkey_access_permitted
if (!is_pkey_enabled(pkey))
return true
return false
pkey_access_permitted() should not check if the pkey is available in
UAMOR (using is_pkey_enabled()). The kernel needs to do that check
only when allocating keys. This also makes sure the execute_only_key
which is marked as non-manageable via UAMOR is handled correctly in
pkey_access_permitted(), and fixes the bug.
Fixes: c46241a370 ("powerpc/pkeys: Check vma before returning key fault error to the user")
Reported-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
[mpe: Include bug report details etc. in the change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200627070147.297535-1-aneesh.kumar@linux.ibm.com
19ab500edb