[PATCH 4.4 078/158] parisc: Fix kernel panic due invalid values in IAOQ0 or IAOQ1

Greg Kroah-Hartman
2019-08-02T09:32:58Z

From: Helge Deller <deller@gmx.de>

commit 10835c854685393a921b68f529bf740fa7c9984d upstream.

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 in the native and compat ptrace paths.

Link: https://bugs.gentoo.org/481768
Reported-by: Jeroen Roovers <jer@gentoo.org>
Cc: <stable@vger.kernel.org>
Tested-by: Rolf Eike Beer <eike-kernel@sf-tec.de>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/parisc/kernel/ptrace.c | 28 ++++++++++++++++++----------
1 file changed, 18 insertions(+), 10 deletions(-)

--- a/arch/parisc/kernel/ptrace.c
+++ b/arch/parisc/kernel/ptrace.c
@@ -156,6 +156,9 @@ long arch_ptrace(struct task_struct *chi
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) ||
@@ -189,16 +192,18 @@ long arch_ptrace(struct task_struct *chi

static compat_ulong_t translate_usr_offset(compat_ulong_t offset)
{
- if (offset < 0)
- return sizeof(struct pt_regs);
- else if (offset <= 32*4) /* gr[0..31] */
- return offset * 2 + 4;
- else if (offset <= 32*4+32*8) /* gr[0..31] + fr[0..31] */
- return offset + 32*4;
- else if (offset < sizeof(struct pt_regs)/2 + 32*4)
- return offset * 2 + 4 - 32*8;
+ compat_ulong_t pos;
+
+ if (offset < 32*4) /* gr[0..31] */
+ pos = offset * 2 + 4;
+ else if (offset < 32*4+32*8) /* fr[0] ... fr[31] */
+ pos = (offset - 32*4) + PT_FR0;
+ else if (offset < sizeof(struct pt_regs)/2 + 32*4) /* sr[0] ... ipsw */
+ pos = (offset - 32*4 - 32*8) * 2 + PT_SR0 + 4;
else
- return sizeof(struct pt_regs);
+ pos = sizeof(struct pt_regs);
+
+ return pos;
}

long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
@@ -242,9 +247,12 @@ long compat_arch_ptrace(struct task_stru
addr = translate_usr_offset(addr);
if (addr >= sizeof(struct pt_regs))
break;
+ if (addr == PT_IAOQ0+4 || addr == PT_IAOQ1+4) {
+ 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;
+ *(__u32 *) ((char *) task_regs(child) + addr) = data;
ret = 0;
}
else if ((addr >= PT_GR1+4 && addr <= PT_GR31+4) ||