diff mbox series

[4.19,26/38] parisc: Correct completer in lws start

Message ID 20211227151320.254627160@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH Dec. 27, 2021, 3:31 p.m. UTC 
From: John David Anglin <dave.anglin@bell.net>

commit 8f66fce0f46560b9e910787ff7ad0974441c4f9c upstream.

The completer in the "or,ev %r1,%r30,%r30" instruction is reversed, so we are
not clipping the LWS number when we are called from a 32-bit process (W=0).
We need to nulify the following depdi instruction when the least-significant
bit of %r30 is 1.

If the %r20 register is not clipped, a user process could perform a LWS call
that would branch to an undefined location in the kernel and potentially crash
the machine.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # 4.19+
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/parisc/kernel/syscall.S |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -478,7 +478,7 @@  lws_start:
 	extrd,u	%r1,PSW_W_BIT,1,%r1
 	/* sp must be aligned on 4, so deposit the W bit setting into
 	 * the bottom of sp temporarily */
-	or,ev	%r1,%r30,%r30
+	or,od	%r1,%r30,%r30
 
 	/* Clip LWS number to a 32-bit value for 32-bit processes */
 	depdi	0, 31, 32, %r20