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, 115 insertions, 0 deletions

diff --git a/fs/squashfs/id.c b/fs/squashfs/id.c
new file mode 100644
index 000000000..ea5387679
--- /dev/null
+++ b/fs/squashfs/id.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
+ * Phillip Lougher <phillip@squashfs.org.uk>
+ *
+ * id.c
+ */
+
+/*
+ * This file implements code to handle uids and gids.
+ *
+ * For space efficiency regular files store uid and gid indexes, which are
+ * converted to 32-bit uids/gids using an id look up table.  This table is
+ * stored compressed into metadata blocks.  A second index table is used to
+ * locate these.  This second index table for speed of access (and because it
+ * is small) is read at mount time and cached in memory.
+ */
+
+#include <linux/fs.h>
+#include <linux/vfs.h>
+#include <linux/slab.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs.h"
+
+/*
+ * Map uid/gid index into real 32-bit uid/gid using the id look up table
+ */
+int squashfs_get_id(struct super_block *sb, unsigned int index,
+					unsigned int *id)
+{
+	struct squashfs_sb_info *msblk = sb->s_fs_info;
+	int block = SQUASHFS_ID_BLOCK(index);
+	int offset = SQUASHFS_ID_BLOCK_OFFSET(index);
+	u64 start_block;
+	__le32 disk_id;
+	int err;
+
+	if (index >= msblk->ids)
+		return -EINVAL;
+
+	start_block = le64_to_cpu(msblk->id_table[block]);
+
+	err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
+							sizeof(disk_id));
+	if (err < 0)
+		return err;
+
+	*id = le32_to_cpu(disk_id);
+	return 0;
+}
+
+
+/*
+ * Read uncompressed id lookup table indexes from disk into memory
+ */
+__le64 *squashfs_read_id_index_table(struct super_block *sb,
+		u64 id_table_start, u64 next_table, unsigned short no_ids)
+{
+	unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
+	unsigned int indexes = SQUASHFS_ID_BLOCKS(no_ids);
+	int n;
+	__le64 *table;
+	u64 start, end;
+
+	TRACE("In read_id_index_table, length %d\n", length);
+
+	/* Sanity check values */
+
+	/* there should always be at least one id */
+	if (no_ids == 0)
+		return ERR_PTR(-EINVAL);
+
+	/*
+	 * The computed size of the index table (length bytes) should exactly
+	 * match the table start and end points
+	 */
+	if (length != (next_table - id_table_start))
+		return ERR_PTR(-EINVAL);
+
+	table = squashfs_read_table(sb, id_table_start, length);
+	if (IS_ERR(table))
+		return table;
+
+	/*
+	 * table[0], table[1], ... table[indexes - 1] store the locations
+	 * of the compressed id blocks.   Each entry should be less than
+	 * the next (i.e. table[0] < table[1]), and the difference between them
+	 * should be SQUASHFS_METADATA_SIZE or less.  table[indexes - 1]
+	 * should be less than id_table_start, and again the difference
+	 * should be SQUASHFS_METADATA_SIZE or less
+	 */
+	for (n = 0; n < (indexes - 1); n++) {
+		start = le64_to_cpu(table[n]);
+		end = le64_to_cpu(table[n + 1]);
+
+		if (start >= end || (end - start) >
+				(SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
+			kfree(table);
+			return ERR_PTR(-EINVAL);
+		}
+	}
+
+	start = le64_to_cpu(table[indexes - 1]);
+	if (start >= id_table_start || (id_table_start - start) >
+				(SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
+		kfree(table);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return table;
+}