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Date: Fri, 31 Aug 2018 10:27:14 +0200 From: Luc Van Oostenryck <luc.vanoostenryck@...il.com> To: Jann Horn <jannh@...gle.com> Cc: Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>, Borislav Petkov <bp@...e.de> Subject: Re: [PATCH] x86/dumpstack: fix address space casting in show_opcodes() On Thu, Aug 30, 2018 at 09:47:36PM +0200, Jann Horn wrote: > I sloppily passed a kernel-typed pointer to __range_not_ok(), and sparse > doesn't like that. > Make `prologue` a __user pointer (to protect against accidental > dereferences) and force-cast it to a kernel pointer when calling > probe_kernel_read(), which will then immediately force-cast it back to a > user pointer. It's a bit sad to have to do this. __range_not_ok() explicitly requires a __user pointer (I don't know if there is a good reason for it) but the real job is done by __chk_range_not_ok(). Can't you use this later instead? -- Luc Van Oostenryck
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