On parisc the privilege level of a process is stored in the lowest two bits of the instruction pointers (IAOQ0 and IAOQ1). On Linux we use privilege level 0 for the kernel and privilege level 3 for user-space. So userspace should not be allowed to modify IAOQ0 or IAOQ1 of a ptraced process to change it's privilege level to e.g. 0 to try to gain kernel privileges. This patch prevents such modifications in the regset support functions by always setting the two lowest bits to one (which relates to privilege level 3 for user-space) if IAOQ0 or IAOQ1 are modified via ptrace regset calls. Link: https://bugs.gentoo.org/481768 Cc: <stable@xxxxxxxxxxxxxxx> # v4.7+ Signed-off-by: Helge Deller <deller@xxxxxx> diff --git a/arch/parisc/kernel/ptrace.c b/arch/parisc/kernel/ptrace.c index c60229075a33..4fa0d4c07521 100644 --- a/arch/parisc/kernel/ptrace.c +++ b/arch/parisc/kernel/ptrace.c @@ -502,7 +510,8 @@ static void set_reg(struct pt_regs *regs, int num, unsigned long val) return; case RI(iaoq[0]): case RI(iaoq[1]): - regs->iaoq[num - RI(iaoq[0])] = val; + /* set 2 lowest bits to ensure userspace privilege: */ + regs->iaoq[num - RI(iaoq[0])] = val | 3; return; case RI(sar): regs->sar = val; return;
