Commit 5403c45a authored by Helge Deller's avatar Helge Deller Committed by Greg Kroah-Hartman

parisc: Ensure userspace privilege for ptraced processes in regset functions

commit 34c32fc6 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 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@vger.kernel.org> # v4.7+
Tested-by: default avatarRolf Eike Beer <eike-kernel@sf-tec.de>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8e6d99ab
...@@ -496,7 +496,8 @@ static void set_reg(struct pt_regs *regs, int num, unsigned long val) ...@@ -496,7 +496,8 @@ static void set_reg(struct pt_regs *regs, int num, unsigned long val)
return; return;
case RI(iaoq[0]): case RI(iaoq[0]):
case RI(iaoq[1]): 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; return;
case RI(sar): regs->sar = val; case RI(sar): regs->sar = val;
return; return;
......
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