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-rw-r--r--fs/squashfs/id.c115
1 files changed, 115 insertions, 0 deletions
diff --git a/fs/squashfs/id.c b/fs/squashfs/id.c
new file mode 100644
index 0000000000..ea53876797
--- /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;
+}