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parisc: Fix kernel panic due invalid values in IAOQ0 or IAOQ1 

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>
This commit is contained in:
Helge Deller 2019-07-16 21:43:11 +02:00
parent c309b6f242
commit 10835c8546
1 changed files with 18 additions and 10 deletions
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28
arch/parisc/kernel/ptrace.c
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@ -167,6 +167,9 @@ 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) ||
@ -228,16 +231,18 @@ long arch_ptrace(struct task_struct *child, long request,
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,
@ -281,9 +286,12 @@ 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+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) ||