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842a0d95ef
commit fe24e27128252c230a34a6c628da2bf1676781ea upstream. Peter Zijlstra's patch for converting WARN() to use UD2 triggered a bunch of false "unreachable instruction" warnings, which then triggered a seg fault in ignore_unreachable_insn(). The seg fault happened when it tried to dereference a NULL 'insn->func' pointer. Thanks to static_cpu_has(), some functions can jump to a non-function area in the .altinstr_aux section. That breaks ignore_unreachable_insn()'s assumption that it's always inside the original function. Make sure ignore_unreachable_insn() only follows jumps within the current function. Reported-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kbuild test robot <fengguang.wu@intel.com> Link: http://lkml.kernel.org/r/bace77a60d5af9b45eddb8f8fb9c776c8de657ef.1518130694.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>