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, 123 insertions, 0 deletions

diff --git a/fs/squashfs/lzo_wrapper.c b/fs/squashfs/lzo_wrapper.c
new file mode 100644
index 000000000..be1df7a25
--- /dev/null
+++ b/fs/squashfs/lzo_wrapper.c
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2010 LG Electronics
+ * Chan Jeong <chan.jeong@lge.com>
+ *
+ * lzo_wrapper.c
+ */
+
+#include <linux/mutex.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/lzo.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs.h"
+#include "decompressor.h"
+#include "page_actor.h"
+
+struct squashfs_lzo {
+	void	*input;
+	void	*output;
+};
+
+static void *lzo_init(struct squashfs_sb_info *msblk, void *buff)
+{
+	int block_size = max_t(int, msblk->block_size, SQUASHFS_METADATA_SIZE);
+
+	struct squashfs_lzo *stream = kzalloc_obj(*stream);
+	if (stream == NULL)
+		goto failed;
+	stream->input = vmalloc(block_size);
+	if (stream->input == NULL)
+		goto failed;
+	stream->output = vmalloc(block_size);
+	if (stream->output == NULL)
+		goto failed2;
+
+	return stream;
+
+failed2:
+	vfree(stream->input);
+failed:
+	ERROR("Failed to allocate lzo workspace\n");
+	kfree(stream);
+	return ERR_PTR(-ENOMEM);
+}
+
+
+static void lzo_free(void *strm)
+{
+	struct squashfs_lzo *stream = strm;
+
+	if (stream) {
+		vfree(stream->input);
+		vfree(stream->output);
+	}
+	kfree(stream);
+}
+
+
+static int lzo_uncompress(struct squashfs_sb_info *msblk, void *strm,
+	struct bio *bio, int offset, int length,
+	struct squashfs_page_actor *output)
+{
+	struct bvec_iter_all iter_all = {};
+	struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
+	struct squashfs_lzo *stream = strm;
+	void *buff = stream->input, *data;
+	int bytes = length, res;
+	size_t out_len = output->length;
+
+	while (bio_next_segment(bio, &iter_all)) {
+		int avail = min(bytes, ((int)bvec->bv_len) - offset);
+
+		data = bvec_virt(bvec);
+		memcpy(buff, data + offset, avail);
+		buff += avail;
+		bytes -= avail;
+		offset = 0;
+	}
+
+	res = lzo1x_decompress_safe(stream->input, (size_t)length,
+					stream->output, &out_len);
+	if (res != LZO_E_OK)
+		goto failed;
+
+	res = bytes = (int)out_len;
+	data = squashfs_first_page(output);
+	buff = stream->output;
+	while (data) {
+		if (bytes <= PAGE_SIZE) {
+			if (!IS_ERR(data))
+				memcpy(data, buff, bytes);
+			break;
+		} else {
+			if (!IS_ERR(data))
+				memcpy(data, buff, PAGE_SIZE);
+			buff += PAGE_SIZE;
+			bytes -= PAGE_SIZE;
+			data = squashfs_next_page(output);
+		}
+	}
+	squashfs_finish_page(output);
+
+	return res;
+
+failed:
+	return -EIO;
+}
+
+const struct squashfs_decompressor squashfs_lzo_comp_ops = {
+	.init = lzo_init,
+	.free = lzo_free,
+	.decompress = lzo_uncompress,
+	.id = LZO_COMPRESSION,
+	.name = "lzo",
+	.alloc_buffer = 0,
+	.supported = 1
+};