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Message-Id: <5ec59addf4d5ee9ed8dc51f9e927867534d0f911.1466974736.git.luto@kernel.org>
Date: Sun, 26 Jun 2016 14:55:35 -0700
From: Andy Lutomirski <luto@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org,
Borislav Petkov <bp@...en8.de>,
Nadav Amit <nadav.amit@...il.com>,
Kees Cook <keescook@...omium.org>,
Brian Gerst <brgerst@...il.com>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Jann Horn <jann@...jh.net>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v4 13/29] x86/dumpstack: Try harder to get a call trace on stack overflow
If we overflow the stack, print_context_stack will abort. Detect
this case and rewind back into the valid part of the stack so that
we can trace it.
Reviewed-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
arch/x86/kernel/dumpstack.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 0d05f113805e..8a2113dfc154 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -87,7 +87,7 @@ static inline int valid_stack_ptr(struct task_struct *task,
else
return 0;
}
- return p > t && p < t + THREAD_SIZE - size;
+ return p >= t && p < t + THREAD_SIZE - size;
}
unsigned long
@@ -98,6 +98,14 @@ print_context_stack(struct task_struct *task,
{
struct stack_frame *frame = (struct stack_frame *)bp;
+ /*
+ * If we overflowed the stack into a guard page, jump back to the
+ * bottom of the usable stack.
+ */
+ if ((unsigned long)task_stack_page(task) - (unsigned long)stack <
+ PAGE_SIZE)
+ stack = (unsigned long *)task_stack_page(task);
+
while (valid_stack_ptr(task, stack, sizeof(*stack), end)) {
unsigned long addr;
--
2.7.4
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