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A crash was observed in the ORC unwinder: BUG: stack guard page was hit at 000000000dd984a2 (stack is 00000000d1caafca..00000000613712f0) kernel stack overflow (page fault): 0000 [#1] SMP NOPTI CPU: 93 PID: 23787 Comm: context_switch1 Not tainted 5.4.145 #1 RIP: 0010:unwind_next_frame Call Trace: <NMI> perf_callchain_kernel get_perf_callchain perf_callchain perf_prepare_sample perf_event_output_forward __perf_event_overflow perf_ibs_handle_irq perf_ibs_nmi_handler nmi_handle default_do_nmi do_nmi end_repeat_nmi This was really two bugs: 1) The perf IBS code passed inconsistent regs to the unwinder. 2) The unwinder didn't handle the bad input gracefully. Fix the latter bug. The ORC unwinder needs to be immune against bad inputs. The problem is that stack_access_ok() doesn't recheck the validity of the full range of registers after switching to the next valid stack with get_stack_info(). Fix that. [ jpoimboe: rewrote commit log ] Signed-off-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lore.kernel.org/r/1650353656-956624-1-git-send-email-dmtrmonakhov@yandex-team.ru Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.