[src/trunk]: src/sys/kern Rewrite kasan_mark() to fix a still existing race i...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/6f354de8aef6
branches:  trunk
changeset: 998844:6f354de8aef6
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat May 04 17:19:10 2019 +0000

description:
Rewrite kasan_mark() to fix a still existing race in pool_cache_get_paddr()
that could cause false positives. Now a buffer initially valid remains
valid, with no invalid->valid dance.

diffstat:

 sys/kern/subr_asan.c |  41 ++++++++++++++++++++++++++---------------
 1 files changed, 26 insertions(+), 15 deletions(-)

diffs (69 lines):

diff -r 7441cb0def57 -r 6f354de8aef6 sys/kern/subr_asan.c
--- a/sys/kern/subr_asan.c      Sat May 04 17:03:39 2019 +0000
+++ b/sys/kern/subr_asan.c      Sat May 04 17:19:10 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_asan.c,v 1.8 2019/05/04 10:07:10 maxv Exp $       */
+/*     $NetBSD: subr_asan.c,v 1.9 2019/05/04 17:19:10 maxv Exp $       */
 
 /*
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_asan.c,v 1.8 2019/05/04 10:07:10 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_asan.c,v 1.9 2019/05/04 17:19:10 maxv Exp $");
 
 #include <sys/param.h>
 #include <sys/device.h>
@@ -237,17 +237,6 @@
        *size += KASAN_SHADOW_SCALE_SIZE;
 }
 
-static void
-kasan_markmem(const void *addr, size_t size, bool valid, uint8_t code)
-{
-       KASSERT((vaddr_t)addr % KASAN_SHADOW_SCALE_SIZE == 0);
-       if (valid) {
-               kasan_shadow_Nbyte_markvalid(addr, size);
-       } else {
-               kasan_shadow_Nbyte_fill(addr, size, code);
-       }
-}
-
 void
 kasan_softint(struct lwp *l)
 {
@@ -268,8 +257,30 @@
 void
 kasan_mark(const void *addr, size_t size, size_t sz_with_redz, uint8_t code)
 {
-       kasan_markmem(addr, sz_with_redz, false, code);
-       kasan_markmem(addr, size, true, code);
+       size_t i, n, redz;
+       int8_t *shad;
+
+       KASSERT((vaddr_t)addr % KASAN_SHADOW_SCALE_SIZE == 0);
+       redz = sz_with_redz - roundup(size, KASAN_SHADOW_SCALE_SIZE);
+       KASSERT(redz % KASAN_SHADOW_SCALE_SIZE == 0);
+       shad = kasan_md_addr_to_shad(addr);
+
+       /* Chunks of 8 bytes, valid. */
+       n = size / KASAN_SHADOW_SCALE_SIZE;
+       for (i = 0; i < n; i++) {
+               *shad++ = 0;
+       }
+
+       /* Possibly one chunk, mid. */
+       if ((size & KASAN_SHADOW_MASK) != 0) {
+               *shad++ = (size & KASAN_SHADOW_MASK);
+       }
+
+       /* Chunks of 8 bytes, invalid. */
+       n = redz / KASAN_SHADOW_SCALE_SIZE;
+       for (i = 0; i < n; i++) {
+               *shad++ = code;
+       }
 }
 
 /* -------------------------------------------------------------------------- */