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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Michael Ellerman <mpe@ellerman.id.au>
Subject: [PATCH 5.9 290/391] powerpc/powermac: Fix low_sleep_handler with KUAP and KUEP
Date:   Tue,  3 Nov 2020 21:35:41 +0100
Message-Id: <20201103203406.620753101@linuxfoundation.org>
In-Reply-To: <20201103203348.153465465@linuxfoundation.org>
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From: Christophe Leroy <christophe.leroy@csgroup.eu>

commit 2c637d2df4ee4830e9d3eb2bd5412250522ce96e upstream.

low_sleep_handler() has an hardcoded restore of segment registers
that doesn't take KUAP and KUEP into account.

Use head_32's load_segment_registers() routine instead.

Fixes: a68c31fc01ef ("powerpc/32s: Implement Kernel Userspace Access Protection")
Fixes: 31ed2b13c48d ("powerpc/32s: Implement Kernel Userspace Execution Prevention.")
Cc: stable@vger.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/21b05f7298c1b18f73e6e5b4cd5005aafa24b6da.1599820109.git.christophe.leroy@csgroup.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/kernel/head_32.S           |    2 +-
 arch/powerpc/platforms/powermac/sleep.S |    9 +--------
 2 files changed, 2 insertions(+), 9 deletions(-)

--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -1002,7 +1002,7 @@ BEGIN_MMU_FTR_SECTION
 END_MMU_FTR_SECTION_IFSET(MMU_FTR_USE_HIGH_BATS)
 	blr
 
-load_segment_registers:
+_GLOBAL(load_segment_registers)
 	li	r0, NUM_USER_SEGMENTS /* load up user segment register values */
 	mtctr	r0		/* for context 0 */
 	li	r3, 0		/* Kp = 0, Ks = 0, VSID = 0 */
--- a/arch/powerpc/platforms/powermac/sleep.S
+++ b/arch/powerpc/platforms/powermac/sleep.S
@@ -294,14 +294,7 @@ grackle_wake_up:
 	 * we do any r1 memory access as we are not sure they
 	 * are in a sane state above the first 256Mb region
 	 */
-	li	r0,16		/* load up segment register values */
-	mtctr	r0		/* for context 0 */
-	lis	r3,0x2000	/* Ku = 1, VSID = 0 */
-	li	r4,0
-3:	mtsrin	r3,r4
-	addi	r3,r3,0x111	/* increment VSID */
-	addis	r4,r4,0x1000	/* address of next segment */
-	bdnz	3b
+	bl	load_segment_registers
 	sync
 	isync