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Aneesh Kumar K.V 62c1cf71a2 powerpc/book3s64/pkeys: Fix pkey_access_permitted() for execute disable pkey 
commit 192b6a7805 upstream.

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: f2407ef3ba ("powerpc: helper to validate key-access permissions of a pte")
Cc: stable@vger.kernel.org # v4.16+
Reported-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
[mpe: Add detail to change log, tweak wording & formatting]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200712132047.1038594-1-aneesh.kumar@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-07-22 09:32:11 +02:00
arch powerpc/book3s64/pkeys: Fix pkey_access_permitted() for execute disable pkey 2020-07-22 09:32:11 +02:00
block block: release bip in a right way in error path 2020-07-16 08:17:23 +02:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: af_alg - fix use-after-free in af_alg_accept() due to bh_lock_sock() 2020-07-09 09:37:10 +02:00
Documentation doc: dt: bindings: usb: dwc3: Update entries for disabling SS instances in park mode 2020-07-22 09:32:04 +02:00
drivers hwmon: (emc2103) fix unable to change fan pwm1_enable attribute 2020-07-22 09:32:11 +02:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs fuse: Fix parameter for FS_IOC_{GET,SET}FLAGS 2020-07-22 09:32:10 +02:00
include virt: vbox: Fix VBGL_IOCTL_VMMDEV_REQUEST_BIG and _LOG req numbers to match upstream 2020-07-22 09:32:09 +02:00
init x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:18:49 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:18:40 +02:00
kernel timer: Fix wheel index calculation on last level 2020-07-22 09:32:11 +02:00
lib lib/zlib: remove outdated and incorrect pre-increment optimization 2020-06-25 15:33:02 +02:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm/slub: fix stack overruns with SLUB_STATS 2020-07-09 09:37:09 +02:00
net sched: consistently handle layer3 header accesses in the presence of VLANs 2020-07-22 09:32:00 +02:00
samples samples: bpf: Fix build error 2020-06-03 08:19:31 +02:00
scripts kbuild: improve cc-option to clean up all temporary files 2020-06-30 23:17:15 -04:00
security apparmor: ensure that dfa state tables have entries 2020-07-22 09:32:06 +02:00
sound ALSA: hda/realtek - Enable Speaker for ASUS UX533 and UX534 2020-07-22 09:32:08 +02:00
tools perf stat: Zero all the 'ena' and 'run' array slot stats for interval mode 2020-07-22 09:32:06 +02:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt KVM: arm64: Synchronize sysreg state on injecting an AArch32 exception 2020-06-22 09:05:09 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 16:38:49 +01:00
Makefile Linux 4.19.133 2020-07-16 08:17:28 +02:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.