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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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192b6a7805
Even if the IAMR value denies execute access, the current code returns
true from pkey_access_permitted() for an execute permission check, if
the AMR read pkey bit is cleared.
This results in repeated page fault loop with a test like below:
#define _GNU_SOURCE
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <inttypes.h>
#include <assert.h>
#include <malloc.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/mman.h>
#ifdef SYS_pkey_mprotect
#undef SYS_pkey_mprotect
#endif
#ifdef SYS_pkey_alloc
#undef SYS_pkey_alloc
#endif
#ifdef SYS_pkey_free
#undef SYS_pkey_free
#endif
#undef PKEY_DISABLE_EXECUTE
#define PKEY_DISABLE_EXECUTE 0x4
#define SYS_pkey_mprotect 386
#define SYS_pkey_alloc 384
#define SYS_pkey_free 385
#define PPC_INST_NOP 0x60000000
#define PPC_INST_BLR 0x4e800020
#define PROT_RWX (PROT_READ | PROT_WRITE | PROT_EXEC)
static int sys_pkey_mprotect(void *addr, size_t len, int prot, int pkey)
{
return syscall(SYS_pkey_mprotect, addr, len, prot, pkey);
}
static int sys_pkey_alloc(unsigned long flags, unsigned long access_rights)
{
return syscall(SYS_pkey_alloc, flags, access_rights);
}
static int sys_pkey_free(int pkey)
{
return syscall(SYS_pkey_free, pkey);
}
static void do_execute(void *region)
{
/* jump to region */
asm volatile(
"mtctr %0;"
"bctrl"
: : "r"(region) : "ctr", "lr");
}
static void do_protect(void *region)
{
size_t pgsize;
int i, pkey;
pgsize = getpagesize();
pkey = sys_pkey_alloc(0, PKEY_DISABLE_EXECUTE);
assert (pkey > 0);
/* perform mprotect */
assert(!sys_pkey_mprotect(region, pgsize, PROT_RWX, pkey));
do_execute(region);
/* free pkey */
assert(!sys_pkey_free(pkey));
}
int main(int argc, char **argv)
{
size_t pgsize, numinsns;
unsigned int *region;
int i;
/* allocate memory region to protect */
pgsize = getpagesize();
region = memalign(pgsize, pgsize);
assert(region != NULL);
assert(!mprotect(region, pgsize, PROT_RWX));
/* fill page with NOPs with a BLR at the end */
numinsns = pgsize / sizeof(region[0]);
for (i = 0; i < numinsns - 1; i++)
region[i] = PPC_INST_NOP;
region[i] = PPC_INST_BLR;
do_protect(region);
return EXIT_SUCCESS;
}
The fix is to only check the IAMR for an execute check, the AMR value
is not relevant.
Fixes:
|
||
|---|---|---|
| .. | ||
| book3s32 | ||
| book3s64 | ||
| kasan | ||
| nohash | ||
| ptdump | ||
| copro_fault.c | ||
| dma-noncoherent.c | ||
| drmem.c | ||
| fault.c | ||
| highmem.c | ||
| hugetlbpage.c | ||
| init_32.c | ||
| init_64.c | ||
| init-common.c | ||
| ioremap_32.c | ||
| ioremap_64.c | ||
| ioremap.c | ||
| Makefile | ||
| mem.c | ||
| mmap.c | ||
| mmu_context.c | ||
| mmu_decl.h | ||
| numa.c | ||
| pgtable_32.c | ||
| pgtable_64.c | ||
| pgtable-frag.c | ||
| pgtable.c | ||
| slice.c | ||