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Explicitly unpoison the stack when entering a softint.

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Softints are the only place where we "discard" a part of the stack: we may
have left the thread without allowing the asan instrumentation to clear
the poison, and in this case, we can get false positives when we hit a
poisoned area of the stack while executing another handler within the same
softint thread.

(I was actually getting a rare false positive in ip6intr.)
This commit is contained in:
maxv 2018-08-22 17:04:36 +00:00
parent 008bce6ffe
commit 2ef4334b7d
2 changed files with 24 additions and 3 deletions
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13
sys/arch/amd64/amd64/asan.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: asan.c,v 1.3 2018/08/22 12:07:42 maxv Exp $ */
/* $NetBSD: asan.c,v 1.4 2018/08/22 17:04:36 maxv Exp $ */
/*
* Copyright (c) 2018 The NetBSD Foundation, Inc.
@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: asan.c,v 1.3 2018/08/22 12:07:42 maxv Exp $");
__KERNEL_RCSID(0, "$NetBSD: asan.c,v 1.4 2018/08/22 17:04:36 maxv Exp $");
#include <sys/param.h>
#include <sys/device.h>
@ -59,6 +59,7 @@ __KERNEL_RCSID(0, "$NetBSD: asan.c,v 1.3 2018/08/22 12:07:42 maxv Exp $");
#define __RET_ADDR (unsigned long)__builtin_return_address(0)
void kasan_softint(struct lwp *);
void kasan_shadow_map(void *, size_t);
void kasan_early_init(void);
void kasan_init(void);
@ -322,6 +323,14 @@ kasan_markmem(const void *addr, size_t size, bool valid)
}
}
void
kasan_softint(struct lwp *l)
{
const void *stk = (const void *)uvm_lwp_getuarea(l);
kasan_shadow_fill(stk, USPACE, 0);
}
void
kasan_alloc(const void *addr, size_t size, size_t sz_with_redz)
{

14
sys/arch/amd64/amd64/spl.S
View File

@ -1,4 +1,4 @@
/* $NetBSD: spl.S,v 1.35 2018/07/14 14:29:40 maxv Exp $ */
/* $NetBSD: spl.S,v 1.36 2018/08/22 17:04:36 maxv Exp $ */
/*
* Copyright (c) 2003 Wasabi Systems, Inc.
@ -65,6 +65,7 @@
*/
#include "opt_ddb.h"
#include "opt_kasan.h"
#define ALIGN_TEXT .align 16,0x90
@ -105,6 +106,17 @@ IDTVEC(softintr)
movq L_PCB(%r15),%rcx
movq %rdi,CPUVAR(CURLWP)
#ifdef KASAN
/* clear the new stack */
pushq %rax
pushq %rdx
pushq %rcx
callq _C_LABEL(kasan_softint)
popq %rcx
popq %rdx
popq %rax
#endif
/* save old context */
movq %rsp,PCB_RSP(%rcx)
movq %rbp,PCB_RBP(%rcx)