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authorThomas Gleixner <tglx@linutronix.de>2019-10-23 20:05:49 +0200
committerThomas Gleixner <tglx@linutronix.de>2019-11-05 00:51:35 +0100
commite361362b08cab1098b64b0e5fd8c879f086b3f46 (patch)
treeb2548347634054b1bc45f813fd8c8050a83cf4f2 /arch/x86
parentfe6f85ca121e9c74e7490fe66b0c5aae38e332c3 (diff)
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
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/dumpstack_64.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 753b8cfe8b8a..87b97897a881 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)