On Mon, Nov 16 2020 at 15:04, Andy Lutomirski wrote: > On Mon, Nov 16, 2020 at 2:01 PM Thomas Gleixner <t...@linutronix.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.
