92 lines
3.5 KiB
Diff
92 lines
3.5 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Andy Lutomirski <luto@kernel.org>
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Date: Mon, 4 Dec 2017 15:07:08 +0100
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Subject: [PATCH] x86/unwinder/orc: Dont bail on stack overflow
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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CVE-2017-5754
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If the stack overflows into a guard page and the ORC unwinder should work
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well: by construction, there can't be any meaningful data in the guard page
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because no writes to the guard page will have succeeded.
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But there is a bug that prevents unwinding from working correctly: if the
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starting register state has RSP pointing into a stack guard page, the ORC
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unwinder bails out immediately.
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Instead of bailing out immediately check whether the next page up is a
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valid check page and if so analyze that. As a result the ORC unwinder will
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start the unwind.
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Tested by intentionally overflowing the task stack. The result is an
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accurate call trace instead of a trace consisting purely of '?' entries.
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There are a few other bugs that are triggered if the unwinder encounters a
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stack overflow after the first step, but they are outside the scope of this
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fix.
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Signed-off-by: Andy Lutomirski <luto@kernel.org>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Cc: Borislav Petkov <bp@alien8.de>
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Cc: Borislav Petkov <bpetkov@suse.de>
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Cc: Brian Gerst <brgerst@gmail.com>
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Cc: Dave Hansen <dave.hansen@intel.com>
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Cc: Dave Hansen <dave.hansen@linux.intel.com>
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Cc: David Laight <David.Laight@aculab.com>
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Cc: Denys Vlasenko <dvlasenk@redhat.com>
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Cc: Eduardo Valentin <eduval@amazon.com>
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Cc: Greg KH <gregkh@linuxfoundation.org>
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Cc: H. Peter Anvin <hpa@zytor.com>
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Cc: Josh Poimboeuf <jpoimboe@redhat.com>
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Cc: Juergen Gross <jgross@suse.com>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Cc: Rik van Riel <riel@redhat.com>
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Cc: Will Deacon <will.deacon@arm.com>
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Cc: aliguori@amazon.com
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Cc: daniel.gruss@iaik.tugraz.at
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Cc: hughd@google.com
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Cc: keescook@google.com
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Link: https://lkml.kernel.org/r/20171204150604.991389777@linutronix.de
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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(cherry picked from commit d3a09104018cf2ad5973dfa8a9c138ef9f5015a3)
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Signed-off-by: Andy Whitcroft <apw@canonical.com>
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Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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(cherry picked from commit e5c3115ac69cddd384d6f7abc4a0ef030b247498)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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arch/x86/kernel/unwind_orc.c | 14 ++++++++++++--
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1 file changed, 12 insertions(+), 2 deletions(-)
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diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
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index 570b70d3f604..cea85bfe93f7 100644
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--- a/arch/x86/kernel/unwind_orc.c
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+++ b/arch/x86/kernel/unwind_orc.c
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@@ -552,8 +552,18 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
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}
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if (get_stack_info((unsigned long *)state->sp, state->task,
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- &state->stack_info, &state->stack_mask))
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- return;
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+ &state->stack_info, &state->stack_mask)) {
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+ /*
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+ * We weren't on a valid stack. It's possible that
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+ * we overflowed a valid stack into a guard page.
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+ * See if the next page up is valid so that we can
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+ * generate some kind of backtrace if this happens.
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+ */
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+ void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp);
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+ if (get_stack_info(next_page, state->task, &state->stack_info,
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+ &state->stack_mask))
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+ return;
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+ }
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/*
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* The caller can provide the address of the first frame directly
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--
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2.14.2
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