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, 129 insertions, 0 deletions

diff --git a/tools/perf/util/lzma.c b/tools/perf/util/lzma.c
new file mode 100644
index 000000000..91b9b5171
--- /dev/null
+++ b/tools/perf/util/lzma.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <errno.h>
+#include <lzma.h>
+#include <stdio.h>
+#include <linux/compiler.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include "compress.h"
+#include "debug.h"
+#include <string.h>
+#include <unistd.h>
+#include <internal/lib.h>
+
+#define BUFSIZE 8192
+
+static const char *lzma_strerror(lzma_ret ret)
+{
+	switch ((int) ret) {
+	case LZMA_MEM_ERROR:
+		return "Memory allocation failed";
+	case LZMA_OPTIONS_ERROR:
+		return "Unsupported decompressor flags";
+	case LZMA_FORMAT_ERROR:
+		return "The input is not in the .xz format";
+	case LZMA_DATA_ERROR:
+		return "Compressed file is corrupt";
+	case LZMA_BUF_ERROR:
+		return "Compressed file is truncated or otherwise corrupt";
+	default:
+		return "Unknown error, possibly a bug";
+	}
+}
+
+int lzma_decompress_stream_to_file(FILE *infile, int output_fd)
+{
+	lzma_action action = LZMA_RUN;
+	lzma_stream strm   = LZMA_STREAM_INIT;
+	lzma_ret ret;
+	int err = -1;
+
+	u8 buf_in[BUFSIZE];
+	u8 buf_out[BUFSIZE];
+
+	ret = lzma_stream_decoder(&strm, UINT64_MAX, LZMA_CONCATENATED);
+	if (ret != LZMA_OK) {
+		pr_debug("lzma: lzma_stream_decoder failed %s (%d)\n", lzma_strerror(ret), ret);
+		return err;
+	}
+
+	strm.next_in   = NULL;
+	strm.avail_in  = 0;
+	strm.next_out  = buf_out;
+	strm.avail_out = sizeof(buf_out);
+
+	while (1) {
+		if (strm.avail_in == 0 && !feof(infile)) {
+			strm.next_in  = buf_in;
+			strm.avail_in = fread(buf_in, 1, sizeof(buf_in), infile);
+
+			if (ferror(infile)) {
+				pr_debug("lzma: read error: %m\n");
+				goto err_lzma_end;
+			}
+
+			if (feof(infile))
+				action = LZMA_FINISH;
+		}
+
+		ret = lzma_code(&strm, action);
+
+		if (strm.avail_out == 0 || ret == LZMA_STREAM_END) {
+			ssize_t write_size = sizeof(buf_out) - strm.avail_out;
+
+			if (writen(output_fd, buf_out, write_size) != write_size) {
+				pr_debug("lzma: write error: %m\n");
+				goto err_lzma_end;
+			}
+
+			strm.next_out  = buf_out;
+			strm.avail_out = sizeof(buf_out);
+		}
+
+		if (ret != LZMA_OK) {
+			if (ret == LZMA_STREAM_END)
+				break;
+
+			pr_debug("lzma: failed %s\n", lzma_strerror(ret));
+			goto err_lzma_end;
+		}
+	}
+
+	err = 0;
+err_lzma_end:
+	lzma_end(&strm);
+	return err;
+}
+
+int lzma_decompress_to_file(const char *input, int output_fd)
+{
+	FILE *infile;
+	int ret;
+
+	infile = fopen(input, "rb");
+	if (!infile) {
+		pr_debug("lzma: fopen failed on %s: '%m'\n", input);
+		return -1;
+	}
+
+	ret = lzma_decompress_stream_to_file(infile, output_fd);
+	fclose(infile);
+	return ret;
+}
+
+bool lzma_is_compressed(const char *input)
+{
+	int fd = open(input, O_RDONLY);
+	const uint8_t magic[6] = { 0xFD, '7', 'z', 'X', 'Z', 0x00 };
+	char buf[6] = { 0 };
+	ssize_t rc;
+
+	if (fd < 0)
+		return false;
+
+	rc = read(fd, buf, sizeof(buf));
+	close(fd);
+	return rc == sizeof(buf) ?
+	       memcmp(buf, magic, sizeof(buf)) == 0 : false;
+}