From 34c32fc603311a72cb558e5e337555434f64c27b Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Thu, 4 Jul 2019 03:44:17 +0200 Subject: [PATCH] parisc: Ensure userspace privilege for ptraced processes in regset functions 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: # v4.7+ Tested-by: Rolf Eike Beer Signed-off-by: Helge Deller --- arch/parisc/kernel/ptrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/parisc/kernel/ptrace.c b/arch/parisc/kernel/ptrace.c index 040ff16dd5e7..9f6ff7bc06f9 100644 --- a/arch/parisc/kernel/ptrace.c +++ b/arch/parisc/kernel/ptrace.c @@ -504,7 +504,8 @@ 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; -- 2.30.2