From: "tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Cyrill Gorcunov <gorcunov@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Josh Poimboeuf <jpoimboe@redhat.com>,
stable@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Borislav Petkov <bp@alien8.de>,
linux-kernel@vger.kernel.org
Subject: [tip: x86/urgent] x86/dumpstack/64: Don't evaluate exception stacks before setup
Date: Mon, 04 Nov 2019 23:56:13 -0000 [thread overview]
Message-ID: <157291177324.29376.14563915167890708264.tip-bot2@tip-bot2> (raw)
In-Reply-To: <alpine.DEB.2.21.1910231950590.1852@nanos.tec.linutronix.de>
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: e361362b08cab1098b64b0e5fd8c879f086b3f46
Gitweb: https://git.kernel.org/tip/e361362b08cab1098b64b0e5fd8c879f086b3f46
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 23 Oct 2019 20:05:49 +02:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Tue, 05 Nov 2019 00:51:35 +01:00
x86/dumpstack/64: Don't evaluate exception stacks before setup
Cyrill reported the following crash:
BUG: unable to handle page fault for address: 0000000000001ff0
#PF: supervisor read access in kernel mode
RIP: 0010:get_stack_info+0xb3/0x148
It turns out that if the stack tracer is invoked before the exception stack
mappings are initialized in_exception_stack() can erroneously classify an
invalid address as an address inside of an exception stack:
begin = this_cpu_read(cea_exception_stacks); <- 0
end = begin + sizeof(exception stacks);
i.e. any address between 0 and end will be considered as exception stack
address and the subsequent code will then try to derefence the resulting
stack frame at a non mapped address.
end = begin + (unsigned long)ep->size;
==> end = 0x2000
regs = (struct pt_regs *)end - 1;
==> regs = 0x2000 - sizeof(struct pt_regs *) = 0x1ff0
info->next_sp = (unsigned long *)regs->sp;
==> Crashes due to accessing 0x1ff0
Prevent this by checking the validity of the cea_exception_stack base
address and bailing out if it is zero.
Fixes: afcd21dad88b ("x86/dumpstack/64: Use cpu_entry_area instead of orig_ist")
Reported-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Cyrill Gorcunov <gorcunov@gmail.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1910231950590.1852@nanos.tec.linutronix.de
---
arch/x86/kernel/dumpstack_64.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 753b8cf..87b9789 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -94,6 +94,13 @@ static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
begin = (unsigned long)__this_cpu_read(cea_exception_stacks);
+ /*
+ * Handle the case where stack trace is collected _before_
+ * cea_exception_stacks had been initialized.
+ */
+ if (!begin)
+ return false;
+
end = begin + sizeof(struct cea_exception_stacks);
/* Bail if @stack is outside the exception stack area. */
if (stk < begin || stk >= end)
prev parent reply other threads:[~2019-11-04 23:56 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-19 11:44 [BUG -tip] kmemleak and stacktrace cause page faul Cyrill Gorcunov
2019-10-22 14:23 ` Cyrill Gorcunov
2019-10-22 14:56 ` Cyrill Gorcunov
2019-10-23 13:21 ` Thomas Gleixner
2019-10-23 13:32 ` Cyrill Gorcunov
2019-10-23 13:38 ` Thomas Gleixner
2019-10-23 13:44 ` Cyrill Gorcunov
2019-10-23 13:47 ` Thomas Gleixner
2019-10-23 13:53 ` Cyrill Gorcunov
2019-10-23 13:59 ` Cyrill Gorcunov
2019-10-23 18:05 ` [PATCH] x86/dumpstack/64: Don't evaluate exception stacks before setup Thomas Gleixner
2019-10-23 18:31 ` Matthew Wilcox
2019-10-23 18:43 ` Cyrill Gorcunov
2019-10-23 21:27 ` Thomas Gleixner
2019-10-23 19:17 ` Josh Poimboeuf
2019-11-04 23:56 ` tip-bot2 for Thomas Gleixner [this message]
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