From: Andy Lutomirski <luto@kernel.org>
To: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
x86@kernel.org, Borislav Petkov <bp@alien8.de>
Cc: Nadav Amit <nadav.amit@gmail.com>,
Kees Cook <keescook@chromium.org>,
Brian Gerst <brgerst@gmail.com>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Andy Lutomirski <luto@kernel.org>
Subject: [PATCH 13/13] x86/mm: Improve stack-overflow #PF handling
Date: Wed, 15 Jun 2016 17:28:35 -0700 [thread overview]
Message-ID: <cd46e564789550d4f093d3cace33489a3855831f.1466036668.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1466036668.git.luto@kernel.org>
In-Reply-To: <cover.1466036668.git.luto@kernel.org>
If we get a page fault indicating kernel stack overflow, invoke
handle_stack_overflow(). To prevent us from overflowing the stack
again while handling the overflow (because we are likely to have
very little stack space left), call handle_stack_overflow() on the
double-fault stack
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/include/asm/traps.h | 6 ++++++
arch/x86/kernel/traps.c | 6 +++---
arch/x86/mm/fault.c | 39 +++++++++++++++++++++++++++++++++++++++
3 files changed, 48 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index c3496619740a..01fd0a7f48cd 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -117,6 +117,12 @@ extern void ist_exit(struct pt_regs *regs);
extern void ist_begin_non_atomic(struct pt_regs *regs);
extern void ist_end_non_atomic(void);
+#ifdef CONFIG_VMAP_STACK
+void __noreturn handle_stack_overflow(const char *message,
+ struct pt_regs *regs,
+ unsigned long fault_address);
+#endif
+
/* Interrupts/Exceptions */
enum {
X86_TRAP_DE = 0, /* 0, Divide-by-zero */
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9cb7ea781176..b389c0539eb9 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -293,9 +293,9 @@ DO_ERROR(X86_TRAP_SS, SIGBUS, "stack segment", stack_segment)
DO_ERROR(X86_TRAP_AC, SIGBUS, "alignment check", alignment_check)
#ifdef CONFIG_VMAP_STACK
-static void __noreturn handle_stack_overflow(const char *message,
- struct pt_regs *regs,
- unsigned long fault_address)
+__visible void __noreturn handle_stack_overflow(const char *message,
+ struct pt_regs *regs,
+ unsigned long fault_address)
{
printk(KERN_EMERG "BUG: stack guard page was hit at %p (stack is %p..%p)\n",
(void *)fault_address, current->stack,
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 7d1fa7cd2374..c68b81f5659f 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -753,6 +753,45 @@ no_context(struct pt_regs *regs, unsigned long error_code,
return;
}
+#ifdef CONFIG_VMAP_STACK
+ /*
+ * Stack overflow? During boot, we can fault near the initial
+ * stack in the direct map, but that's not an overflow -- check
+ * that we're in vmalloc space to avoid this.
+ *
+ * Check this after trying fixup_exception, since there are handful
+ * of kernel code paths that wander off the top of the stack but
+ * handle any faults that occur. Once those are fixed, we can
+ * move this above fixup_exception.
+ */
+ if (is_vmalloc_addr((void *)address) &&
+ (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
+ address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
+ register void *__sp asm("rsp");
+ unsigned long stack =
+ this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) -
+ sizeof(void *);
+ /*
+ * We're likely to be running with very little stack space
+ * left. It's plausible that we'd hit this condition but
+ * double-fault even before we get this far, in which case
+ * we're fine: the double-fault handler will deal with it.
+ *
+ * We don't want to make it all the way into the oops code
+ * and then double-fault, though, because we're likely to
+ * break the console driver and lose most of the stack dump.
+ */
+ asm volatile ("movq %[stack], %%rsp\n\t"
+ "call handle_stack_overflow\n\t"
+ "1: jmp 1b"
+ : "+r" (__sp)
+ : "D" ("kernel stack overflow (page fault)"),
+ "S" (regs), "d" (address),
+ [stack] "rm" (stack));
+ unreachable();
+ }
+#endif
+
/*
* 32-bit:
*
--
2.7.4
next prev parent reply other threads:[~2016-06-16 0:29 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 0:28 [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski
2016-06-16 0:28 ` [PATCH 01/13] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Andy Lutomirski
2016-06-16 0:28 ` [PATCH 02/13] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated Andy Lutomirski
2016-06-16 0:28 ` [PATCH 03/13] x86/cpa: Warn if kernel_unmap_pages_in_pgd is used inappropriately Andy Lutomirski
2016-06-16 0:28 ` [PATCH 04/13] mm: Track NR_KERNEL_STACK in pages instead of number of stacks Andy Lutomirski
2016-06-16 11:10 ` Vladimir Davydov
2016-06-16 17:21 ` Andy Lutomirski
2016-06-16 19:20 ` Andy Lutomirski
2016-06-16 15:33 ` Josh Poimboeuf
2016-06-16 17:39 ` Andy Lutomirski
2016-06-16 19:39 ` Josh Poimboeuf
2016-06-16 0:28 ` [PATCH 05/13] mm: Move memcg stack accounting to account_kernel_stack Andy Lutomirski
2016-06-16 0:28 ` [PATCH 06/13] fork: Add generic vmalloced stack support Andy Lutomirski
2016-06-16 17:25 ` Kees Cook
2016-06-16 17:37 ` Andy Lutomirski
2016-06-16 0:28 ` [PATCH 07/13] x86/die: Don't try to recover from an OOPS on a non-default stack Andy Lutomirski
2016-06-16 0:28 ` [PATCH 08/13] x86/dumpstack: When OOPSing, rewind the stack before do_exit Andy Lutomirski
2016-06-16 17:50 ` Josh Poimboeuf
2016-06-16 17:57 ` Andy Lutomirski
2016-06-16 0:28 ` [PATCH 09/13] x86/dumpstack: When dumping stack bytes due to OOPS, start with regs->sp Andy Lutomirski
2016-06-16 11:56 ` Borislav Petkov
2016-07-08 12:07 ` [tip:x86/debug] x86/dumpstack: Honor supplied @regs arg tip-bot for Andy Lutomirski
2016-06-16 0:28 ` [PATCH 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow Andy Lutomirski
2016-06-16 18:16 ` Josh Poimboeuf
2016-06-16 18:22 ` Andy Lutomirski
2016-06-16 18:33 ` Josh Poimboeuf
2016-06-16 18:37 ` Andy Lutomirski
2016-06-16 18:54 ` Josh Poimboeuf
2016-06-16 0:28 ` [PATCH 11/13] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS Andy Lutomirski
2016-06-16 0:28 ` [PATCH 12/13] x86/mm/64: Enable vmapped stacks Andy Lutomirski
2016-06-16 4:17 ` Mika Penttilä
2016-06-16 5:33 ` Andy Lutomirski
2016-06-16 13:11 ` [kernel-hardening] " Rik van Riel
2016-06-16 0:28 ` Andy Lutomirski [this message]
2016-06-16 6:05 ` [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core) Heiko Carstens
2016-06-16 17:50 ` Andy Lutomirski
2016-06-16 18:14 ` Andy Lutomirski
2016-06-16 21:27 ` Andy Lutomirski
2016-06-17 3:58 ` Andy Lutomirski
2016-06-17 7:27 ` Heiko Carstens
2016-06-17 17:38 ` Andy Lutomirski
2016-06-20 5:58 ` Heiko Carstens
2016-06-20 6:01 ` Andy Lutomirski
2016-06-20 7:07 ` Heiko Carstens
2016-06-16 17:24 ` Kees Cook
2016-07-04 22:31 [PATCH -v2 0/3] x86/MSR: Improve unhandled MSR access error message Borislav Petkov
2016-07-04 22:31 ` [PATCH -v2 1/3] x86/dumpstack: Honor supplied @regs arg Borislav Petkov
2016-07-04 22:31 ` [PATCH -v2 2/3] printk: Make the printk*once() variants return a value Borislav Petkov
2016-07-08 12:08 ` [tip:x86/debug] " tip-bot for Borislav Petkov
2016-07-09 2:40 ` Joe Perches
2016-07-09 7:50 ` Borislav Petkov
2016-07-09 17:56 ` Joe Perches
2016-07-10 6:49 ` Borislav Petkov
2016-07-10 8:23 ` Joe Perches
2016-07-10 12:06 ` Borislav Petkov
2016-07-10 12:33 ` Joe Perches
2016-07-04 22:31 ` [PATCH -v2 3/3] x86/dumpstack: Add show_stack_regs() and use it Borislav Petkov
2016-07-08 12:08 ` [tip:x86/debug] " tip-bot for Borislav Petkov
2016-07-06 12:58 ` [PATCH -v2 0/3] x86/MSR: Improve unhandled MSR access error message Andy Lutomirski
2016-07-06 13:11 ` Borislav Petkov
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