From 19ab500edb5d6020010caba48ce3b4ce4182ab63 Mon Sep 17 00:00:00 2001
From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Date: Sat, 27 Jun 2020 12:31:46 +0530
Subject: [PATCH] powerpc/mm/pkeys: Make pkey access check work on
execute_only_key
References: bsc#1181544 ltc#191080 git-fixes
Patch-mainline: v5.8-rc4
Git-commit: 19ab500edb5d6020010caba48ce3b4ce4182ab63
Jan reported that LTP mmap03 was getting stuck in a page fault loop
after commit c46241a370a6 ("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: c46241a370a6 ("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
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/mm/pkeys.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index 1199fc2bfaec..ca5fcb4bff32 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -353,9 +353,6 @@ static bool pkey_access_permitted(int pkey, bool write, bool execute)
int pkey_shift;
u64 amr;
- if (!is_pkey_enabled(pkey))
- return true;
-
pkey_shift = pkeyshift(pkey);
if (execute && !(read_iamr() & (IAMR_EX_BIT << pkey_shift)))
return true;
--
2.26.2