diff options
| author | Thomas Gleixner | 2019-10-23 20:05:49 +0200 |
|---|---|---|
| committer | Thomas Gleixner | 2019-11-05 00:51:35 +0100 |
| commit | e361362b08cab1098b64b0e5fd8c879f086b3f46 (patch) | |
| tree | b2548347634054b1bc45f813fd8c8050a83cf4f2 | |
| parent | fe6f85ca121e9c74e7490fe66b0c5aae38e332c3 (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
| -rw-r--r-- | arch/x86/kernel/dumpstack_64.c | 7 |
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) |