On Wed, 3 Jul 2019 08:35:24 +0200 Helge Deller <deller@xxxxxx> wrote: > 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 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 calls. > > Fixes: https://bugs.gentoo.org/481768 > Reported-by: Jeroen Roovers <jer@xxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > > diff --git a/arch/parisc/kernel/ptrace.c b/arch/parisc/kernel/ptrace.c > index a3d2fb4e6dd2..8ecd41938709 100644 > --- a/arch/parisc/kernel/ptrace.c > +++ b/arch/parisc/kernel/ptrace.c > @@ -167,6 +175,9 @@ long arch_ptrace(struct task_struct *child, long > request, if ((addr & (sizeof(unsigned long)-1)) || > addr >= sizeof(struct pt_regs)) > break; > + if (addr == PT_IAOQ0 || addr == PT_IAOQ1) { > + data |= 3; /* ensure userspace privilege */ > + } > if ((addr >= PT_GR1 && addr <= PT_GR31) || > addr == PT_IAOQ0 || addr == PT_IAOQ1 > || (addr >= PT_FR0 && addr <= PT_FR31 + 4) || > @@ -281,6 +292,9 @@ long compat_arch_ptrace(struct task_struct > *child, compat_long_t request, addr = translate_usr_offset(addr); > if (addr >= sizeof(struct pt_regs)) > break; > + if (addr == PT_IAOQ0 || addr == PT_IAOQ1) { > + data |= 3; /* ensure userspace > privilege */ > + } > if (addr >= PT_FR0 && addr <= PT_FR31 + 4) { > /* Special case, fp regs are 64 bits > anyway */ *(__u64 *) ((char *) task_regs(child) + addr) = data; That may fix some problem, but it sadly does not fix the problem reported in https://bugs.gentoo.org/481768 . Both root and unprivileged users can still trigger the same kernel panic with a kernel patches thusly. How can we help you reproduce the issue? Kind regards, jer
