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Commit ddc1d49e authored by John David Anglin's avatar John David Anglin Committed by Greg Kroah-Hartman
Browse files

parisc: Correct completer in lws start 



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: default avatarJohn David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # 4.19+
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8467c8cb

arch/parisc/kernel/syscall.S

+1 −1
Original line number Diff line number Diff line
@@ -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