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Date: Mon, 16 Nov 2020 19:29:11 -0800 From: Andy Lutomirski <luto@...nel.org> To: Thomas Gleixner <tglx@...utronix.de> Cc: Borislav Petkov <bp@...en8.de>, Oleg Nesterov <oleg@...hat.com>, Mark Mossberg <mark.mossberg@...il.com>, Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>, "H. Peter Anvin" <hpa@...or.com>, Jann Horn <jannh@...gle.com>, kyin@...hat.com Subject: Re: [PATCH v2] x86/dumpstack: Fix misleading instruction pointer error message On Mon, Nov 16, 2020 at 3:37 PM Thomas Gleixner <tglx@...utronix.de> wrote: > > On Mon, Nov 16 2020 at 15:04, Andy Lutomirski wrote: > > > On Mon, Nov 16, 2020 at 2:01 PM Thomas Gleixner <tglx@...utronix.de> wrote: > >> arch/x86/kernel/dumpstack.c | 23 +++++++++++++++++++---- > >> 1 file changed, 19 insertions(+), 4 deletions(-) > >> > >> --- a/arch/x86/kernel/dumpstack.c > >> +++ b/arch/x86/kernel/dumpstack.c > >> @@ -78,6 +78,9 @@ static int copy_code(struct pt_regs *reg > >> if (!user_mode(regs)) > >> return copy_from_kernel_nofault(buf, (u8 *)src, nbytes); > >> > >> + /* The user space code from other tasks cannot be accessed. */ > >> + if (regs != task_pt_regs(current)) > >> + return -EPERM; > > > > Depending on exactly where this gets called, this may not be > > sufficient. You should also check nmi_uaccess_okay(). > > which is what copy_from_user_nmi() already does. Whoops. I thought I checked that...
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