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    x86/unwind: Disable KASAN checks for non-current tasks · 84936118
    Josh Poimboeuf 提交于
    There are a handful of callers to save_stack_trace_tsk() and
    show_stack() which try to unwind the stack of a task other than current.
    In such cases, it's remotely possible that the task is running on one
    CPU while the unwinder is reading its stack from another CPU, causing
    the unwinder to see stack corruption.
    
    These cases seem to be mostly harmless.  The unwinder has checks which
    prevent it from following bad pointers beyond the bounds of the stack.
    So it's not really a bug as long as the caller understands that
    unwinding another task will not always succeed.
    
    In such cases, it's possible that the unwinder may read a KASAN-poisoned
    region of the stack.  Account for that by using READ_ONCE_NOCHECK() when
    reading the stack of another task.
    
    Use READ_ONCE() when reading the stack of the current task, since KASAN
    warnings can still be useful for finding bugs in that case.
    Reported-by: NDmitry Vyukov <dvyukov@google.com>
    Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Dave Jones <davej@codemonkey.org.uk>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Miroslav Benes <mbenes@suse.cz>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/4c575eb288ba9f73d498dfe0acde2f58674598f1.1483978430.git.jpoimboe@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
    84936118
unwind_frame.c 7.9 KB