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, 29 insertions, 0 deletions

diff --git a/sound/last.c b/sound/last.c
new file mode 100644
index 000000000..f0bb98780
--- /dev/null
+++ b/sound/last.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Advanced Linux Sound Architecture
+ *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
+ */
+
+#include <linux/init.h>
+#include <sound/core.h>
+
+static int __init alsa_sound_last_init(void)
+{
+	struct snd_card *card;
+	int idx, ok = 0;
+	
+	printk(KERN_INFO "ALSA device list:\n");
+	for (idx = 0; idx < SNDRV_CARDS; idx++) {
+		card = snd_card_ref(idx);
+		if (card) {
+			printk(KERN_INFO "  #%i: %s\n", idx, card->longname);
+			snd_card_unref(card);
+			ok++;
+		}
+	}
+	if (ok == 0)
+		printk(KERN_INFO "  No soundcards found.\n");
+	return 0;
+}
+
+late_initcall_sync(alsa_sound_last_init);