openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 183 insertions, 0 deletions

diff --git a/arch/alpha/lib/memmove.S b/arch/alpha/lib/memmove.S
new file mode 100644
index 000000000..3a27689e3
--- /dev/null
+++ b/arch/alpha/lib/memmove.S
@@ -0,0 +1,183 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * arch/alpha/lib/memmove.S
+ *
+ * Barely optimized memmove routine for Alpha EV5.
+ *
+ * This is hand-massaged output from the original memcpy.c.  We defer to
+ * memcpy whenever possible; the backwards copy loops are not unrolled.
+ */
+#include <linux/export.h>
+	.set noat
+	.set noreorder
+	.text
+
+	.align 4
+	.globl memmove
+	.ent memmove
+memmove:
+	ldgp $29, 0($27)
+	unop
+	nop
+	.prologue 1
+
+	addq $16,$18,$4
+	addq $17,$18,$5
+	cmpule $4,$17,$1		/*  dest + n <= src  */
+	cmpule $5,$16,$2		/*  dest >= src + n  */
+
+	bis $1,$2,$1
+	mov $16,$0
+	xor $16,$17,$2
+	bne $1,memcpy			!samegp
+
+	and $2,7,$2			/* Test for src/dest co-alignment.  */
+	and $16,7,$1
+	cmpule $16,$17,$3
+	bne $3,$memmove_up		/* dest < src */
+
+	and $4,7,$1
+	bne $2,$misaligned_dn
+	unop
+	beq $1,$skip_aligned_byte_loop_head_dn
+
+$aligned_byte_loop_head_dn:
+	lda $4,-1($4)
+	lda $5,-1($5)
+	unop
+	ble $18,$egress
+
+	ldq_u $3,0($5)
+	ldq_u $2,0($4)
+	lda $18,-1($18)
+	extbl $3,$5,$1
+
+	insbl $1,$4,$1
+	mskbl $2,$4,$2
+	bis $1,$2,$1
+	and $4,7,$6
+
+	stq_u $1,0($4)
+	bne $6,$aligned_byte_loop_head_dn
+
+$skip_aligned_byte_loop_head_dn:
+	lda $18,-8($18)
+	blt $18,$skip_aligned_word_loop_dn
+
+$aligned_word_loop_dn:
+	ldq $1,-8($5)
+	nop
+	lda $5,-8($5)
+	lda $18,-8($18)
+
+	stq $1,-8($4)
+	nop
+	lda $4,-8($4)
+	bge $18,$aligned_word_loop_dn
+
+$skip_aligned_word_loop_dn:
+	lda $18,8($18)
+	bgt $18,$byte_loop_tail_dn
+	unop
+	ret $31,($26),1
+
+	.align 4
+$misaligned_dn:
+	nop
+	fnop
+	unop
+	beq $18,$egress
+
+$byte_loop_tail_dn:
+	ldq_u $3,-1($5)
+	ldq_u $2,-1($4)
+	lda $5,-1($5)
+	lda $4,-1($4)
+
+	lda $18,-1($18)
+	extbl $3,$5,$1
+	insbl $1,$4,$1
+	mskbl $2,$4,$2
+
+	bis $1,$2,$1
+	stq_u $1,0($4)
+	bgt $18,$byte_loop_tail_dn
+	br $egress
+
+$memmove_up:
+	mov $16,$4
+	mov $17,$5
+	bne $2,$misaligned_up
+	beq $1,$skip_aligned_byte_loop_head_up
+
+$aligned_byte_loop_head_up:
+	unop
+	ble $18,$egress
+	ldq_u $3,0($5)
+	ldq_u $2,0($4)
+
+	lda $18,-1($18)
+	extbl $3,$5,$1
+	insbl $1,$4,$1
+	mskbl $2,$4,$2
+
+	bis $1,$2,$1
+	lda $5,1($5)
+	stq_u $1,0($4)
+	lda $4,1($4)
+
+	and $4,7,$6
+	bne $6,$aligned_byte_loop_head_up
+
+$skip_aligned_byte_loop_head_up:
+	lda $18,-8($18)
+	blt $18,$skip_aligned_word_loop_up
+
+$aligned_word_loop_up:
+	ldq $1,0($5)
+	nop
+	lda $5,8($5)
+	lda $18,-8($18)
+
+	stq $1,0($4)
+	nop
+	lda $4,8($4)
+	bge $18,$aligned_word_loop_up
+
+$skip_aligned_word_loop_up:
+	lda $18,8($18)
+	bgt $18,$byte_loop_tail_up
+	unop
+	ret $31,($26),1
+
+	.align 4
+$misaligned_up:
+	nop
+	fnop
+	unop
+	beq $18,$egress
+
+$byte_loop_tail_up:
+	ldq_u $3,0($5)
+	ldq_u $2,0($4)
+	lda $18,-1($18)
+	extbl $3,$5,$1
+
+	insbl $1,$4,$1
+	mskbl $2,$4,$2
+	bis $1,$2,$1
+	stq_u $1,0($4)
+
+	lda $5,1($5)
+	lda $4,1($4)
+	nop
+	bgt $18,$byte_loop_tail_up
+
+$egress:
+	ret $31,($26),1
+	nop
+	nop
+	nop
+
+	.end memmove
+	EXPORT_SYMBOL(memmove)