squashfs: add support for xattr reading

Add support for listxattr and getxattr.  Also add xattr definitions.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

4 files changed, 342 insertions, 1 deletions

diff --git a/fs/squashfs/Makefile b/fs/squashfs/Makefile
index c0da4a189cc4..56684d464105 100644
--- a/fs/squashfs/Makefile
+++ b/fs/squashfs/Makefile
@@ -5,5 +5,5 @@
 obj-$(CONFIG_SQUASHFS) += squashfs.o
 squashfs-y += block.o cache.o dir.o export.o file.o fragment.o id.o inode.o
 squashfs-y += namei.o super.o symlink.o zlib_wrapper.o decompressor.o
-squashfs-y += xattr_id.o
+squashfs-y += xattr.o xattr_id.o
 
diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
index c654e863d3c0..6fe940cf9011 100644
--- a/fs/squashfs/squashfs_fs.h
+++ b/fs/squashfs/squashfs_fs.h
@@ -46,6 +46,7 @@
 #define SQUASHFS_NAME_LEN               256
 
 #define SQUASHFS_INVALID_FRAG           (0xffffffffU)
+#define SQUASHFS_INVALID_XATTR          (0xffffffffU)
 #define SQUASHFS_INVALID_BLK            (-1LL)
 
 /* Filesystem flags */
@@ -96,6 +97,13 @@
 #define SQUASHFS_LFIFO_TYPE             13
 #define SQUASHFS_LSOCKET_TYPE           14
 
+/* Xattr types */
+#define SQUASHFS_XATTR_USER             0
+#define SQUASHFS_XATTR_TRUSTED          1
+#define SQUASHFS_XATTR_SECURITY         2
+#define SQUASHFS_XATTR_VALUE_OOL        256
+#define SQUASHFS_XATTR_PREFIX_MASK      0xff
+
 /* Flag whether block is compressed or uncompressed, bit is set if block is
  * uncompressed */
 #define SQUASHFS_COMPRESSED_BIT         (1 << 15)
@@ -395,6 +403,17 @@ struct squashfs_fragment_entry {
         unsigned int            unused;
 };
 
+struct squashfs_xattr_entry {
+        __le16                  type;
+        __le16                  size;
+        char                    data[0];
+};
+
+struct squashfs_xattr_val {
+        __le32                  vsize;
+        char                    value[0];
+};
+
 struct squashfs_xattr_id {
         __le64                  xattr;
         __le32                  count;
diff --git a/fs/squashfs/squashfs_fs_i.h b/fs/squashfs/squashfs_fs_i.h
index fbfca30c0c68..d3e3a37f28a1 100644
--- a/fs/squashfs/squashfs_fs_i.h
+++ b/fs/squashfs/squashfs_fs_i.h
@@ -26,6 +26,9 @@
 struct squashfs_inode_info {
         u64             start;
         int             offset;
+        u64             xattr;
+        unsigned int    xattr_size;
+        int             xattr_count;
         union {
                 struct {
                         u64             fragment_block;
diff --git a/fs/squashfs/xattr.c b/fs/squashfs/xattr.c
new file mode 100644
index 000000000000..147ecc3f69e3
--- /dev/null
+++ b/fs/squashfs/xattr.c
@@ -0,0 +1,319 @@
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2010
+ * Phillip Lougher <phillip@lougher.demon.co.uk>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2,
+ * or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * xattr_id.c
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/fs.h>
+#include <linux/vfs.h>
+#include <linux/xattr.h>
+#include <linux/slab.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs_fs_i.h"
+#include "squashfs.h"
+
+static inline struct xattr_handler *squashfs_xattr_handler(int);
+
+ssize_t squashfs_listxattr(struct dentry *d, char *buffer,
+        size_t buffer_size)
+{
+        struct inode *inode = d->d_inode;
+        struct super_block *sb = inode->i_sb;
+        struct squashfs_sb_info *msblk = sb->s_fs_info;
+        u64 start = SQUASHFS_XATTR_BLK(squashfs_i(inode)->xattr)
+                                                 + msblk->xattr_table;
+        int offset = SQUASHFS_XATTR_OFFSET(squashfs_i(inode)->xattr);
+        int count = squashfs_i(inode)->xattr_count;
+        size_t rest = buffer_size;
+        int err;
+
+        /* check that the file system has xattrs */
+        if (msblk->xattr_id_table == NULL)
+                return -EOPNOTSUPP;
+
+        /* loop reading each xattr name */
+        while (count--) {
+                struct squashfs_xattr_entry entry;
+                struct squashfs_xattr_val val;
+                struct xattr_handler *handler;
+                int name_size, prefix_size = 0;
+
+                err = squashfs_read_metadata(sb, &entry, &start, &offset,
+                                                        sizeof(entry));
+                if (err < 0)
+                        goto failed;
+
+                name_size = le16_to_cpu(entry.size);
+                handler = squashfs_xattr_handler(le16_to_cpu(entry.type));
+                if (handler)
+                        prefix_size = handler->list(d, buffer, rest, NULL,
+                                name_size, handler->flags);
+                if (prefix_size) {
+                        if (buffer) {
+                                if (prefix_size + name_size + 1 > rest) {
+                                        err = -ERANGE;
+                                        goto failed;
+                                }
+                                buffer += prefix_size;
+                        }
+                        err = squashfs_read_metadata(sb, buffer, &start,
+                                &offset, name_size);
+                        if (err < 0)
+                                goto failed;
+                        if (buffer) {
+                                buffer[name_size] = '\0';
+                                buffer += name_size + 1;
+                        }
+                        rest -= prefix_size + name_size + 1;
+                } else  {
+                        /* no handler or insuffficient privileges, so skip */
+                        err = squashfs_read_metadata(sb, NULL, &start,
+                                &offset, name_size);
+                        if (err < 0)
+                                goto failed;
+                }
+
+
+                /* skip remaining xattr entry */
+                err = squashfs_read_metadata(sb, &val, &start, &offset,
+                                                sizeof(val));
+                if (err < 0)
+                        goto failed;
+
+                err = squashfs_read_metadata(sb, NULL, &start, &offset,
+                                                le32_to_cpu(val.vsize));
+                if (err < 0)
+                        goto failed;
+        }
+        err = buffer_size - rest;
+
+failed:
+        return err;
+}
+
+
+static int squashfs_xattr_get(struct inode *inode, int name_index,
+        const char *name, void *buffer, size_t buffer_size)
+{
+        struct super_block *sb = inode->i_sb;
+        struct squashfs_sb_info *msblk = sb->s_fs_info;
+        u64 start = SQUASHFS_XATTR_BLK(squashfs_i(inode)->xattr)
+                                                 + msblk->xattr_table;
+        int offset = SQUASHFS_XATTR_OFFSET(squashfs_i(inode)->xattr);
+        int count = squashfs_i(inode)->xattr_count;
+        int name_len = strlen(name);
+        int err, vsize;
+        char *target = kmalloc(name_len, GFP_KERNEL);
+
+        if (target == NULL)
+                return  -ENOMEM;
+
+        /* loop reading each xattr name */
+        for (; count; count--) {
+                struct squashfs_xattr_entry entry;
+                struct squashfs_xattr_val val;
+                int type, prefix, name_size;
+
+                err = squashfs_read_metadata(sb, &entry, &start, &offset,
+                                                        sizeof(entry));
+                if (err < 0)
+                        goto failed;
+
+                name_size = le16_to_cpu(entry.size);
+                type = le16_to_cpu(entry.type);
+                prefix = type & SQUASHFS_XATTR_PREFIX_MASK;
+
+                err = squashfs_read_metadata(sb, target, &start, &offset,
+                                                        name_size);
+                if (err < 0)
+                        goto failed;
+
+                if (prefix == name_index && name_size == name_len &&
+                                        strncmp(target, name, name_size) == 0) {
+                        /* found xattr */
+                        if (type & SQUASHFS_XATTR_VALUE_OOL) {
+                                __le64 xattr;
+                                /* val is a reference to the real location */
+                                err = squashfs_read_metadata(sb, &val, &start,
+                                                &offset, sizeof(val));
+                                if (err < 0)
+                                        goto failed;
+                                err = squashfs_read_metadata(sb, &xattr, &start,
+                                         &offset, sizeof(xattr));
+                                if (err < 0)
+                                        goto failed;
+                                xattr = le64_to_cpu(xattr);
+                                start = SQUASHFS_XATTR_BLK(xattr) +
+                                                        msblk->xattr_table;
+                                offset = SQUASHFS_XATTR_OFFSET(xattr);
+                        }
+                        /* read xattr value */
+                        err = squashfs_read_metadata(sb, &val, &start, &offset,
+                                                        sizeof(val));
+                        if (err < 0)
+                                goto failed;
+
+                        vsize = le32_to_cpu(val.vsize);
+                        if (buffer) {
+                                if (vsize > buffer_size) {
+                                        err = -ERANGE;
+                                        goto failed;
+                                }
+                                err = squashfs_read_metadata(sb, buffer, &start,
+                                         &offset, vsize);
+                                if (err < 0)
+                                        goto failed;
+                        }
+                        break;
+                }
+
+                /* no match, skip remaining xattr entry */
+                err = squashfs_read_metadata(sb, &val, &start, &offset,
+                                                        sizeof(val));
+                if (err < 0)
+                        goto failed;
+                err = squashfs_read_metadata(sb, NULL, &start, &offset,
+                                                le32_to_cpu(val.vsize));
+                if (err < 0)
+                        goto failed;
+        }
+        err = count ? vsize : -ENODATA;
+
+failed:
+        kfree(target);
+        return err;
+}
+
+
+/*
+ * User namespace support
+ */
+static size_t squashfs_user_list(struct dentry *d, char *list, size_t list_size,
+        const char *name, size_t name_len, int type)
+{
+        if (list && XATTR_USER_PREFIX_LEN <= list_size)
+                memcpy(list, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
+        return XATTR_USER_PREFIX_LEN;
+}
+
+static int squashfs_user_get(struct dentry *d, const char *name, void *buffer,
+        size_t size, int type)
+{
+        if (name[0] == '\0')
+                return  -EINVAL;
+
+        return squashfs_xattr_get(d->d_inode, SQUASHFS_XATTR_USER, name,
+                buffer, size);
+}
+
+struct xattr_handler squashfs_xattr_user_handler = {
+        .prefix = XATTR_USER_PREFIX,
+        .list   = squashfs_user_list,
+        .get    = squashfs_user_get
+};
+
+/*
+ * Trusted namespace support
+ */
+static size_t squashfs_trusted_list(struct dentry *d, char *list,
+        size_t list_size, const char *name, size_t name_len, int type)
+{
+        if (!capable(CAP_SYS_ADMIN))
+                return 0;
+
+        if (list && XATTR_TRUSTED_PREFIX_LEN <= list_size)
+                memcpy(list, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
+        return XATTR_TRUSTED_PREFIX_LEN;
+}
+
+static int squashfs_trusted_get(struct dentry *d, const char *name,
+        void *buffer, size_t size, int type)
+{
+        if (name[0] == '\0')
+                return  -EINVAL;
+
+        return squashfs_xattr_get(d->d_inode, SQUASHFS_XATTR_TRUSTED, name,
+                buffer, size);
+}
+
+struct xattr_handler squashfs_xattr_trusted_handler = {
+        .prefix = XATTR_TRUSTED_PREFIX,
+        .list   = squashfs_trusted_list,
+        .get    = squashfs_trusted_get
+};
+
+/*
+ * Security namespace support
+ */
+static size_t squashfs_security_list(struct dentry *d, char *list,
+        size_t list_size, const char *name, size_t name_len, int type)
+{
+        if (list && XATTR_SECURITY_PREFIX_LEN <= list_size)
+                memcpy(list, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN);
+        return XATTR_SECURITY_PREFIX_LEN;
+}
+
+static int squashfs_security_get(struct dentry *d, const char *name,
+        void *buffer, size_t size, int type)
+{
+        if (name[0] == '\0')
+                return  -EINVAL;
+
+        return squashfs_xattr_get(d->d_inode, SQUASHFS_XATTR_SECURITY, name,
+                buffer, size);
+}
+
+struct xattr_handler squashfs_xattr_security_handler = {
+        .prefix = XATTR_SECURITY_PREFIX,
+        .list   = squashfs_security_list,
+        .get    = squashfs_security_get
+};
+
+static inline struct xattr_handler *squashfs_xattr_handler(int type)
+{
+        if (type & ~(SQUASHFS_XATTR_PREFIX_MASK | SQUASHFS_XATTR_VALUE_OOL))
+                /* ignore unrecognised type */
+                return NULL;
+
+        switch (type & SQUASHFS_XATTR_PREFIX_MASK) {
+        case SQUASHFS_XATTR_USER:
+                return &squashfs_xattr_user_handler;
+        case SQUASHFS_XATTR_TRUSTED:
+                return &squashfs_xattr_trusted_handler;
+        case SQUASHFS_XATTR_SECURITY:
+                return &squashfs_xattr_security_handler;
+        default:
+                /* ignore unrecognised type */
+                return NULL;
+        }
+}
+
+struct xattr_handler *squashfs_xattr_handlers[] = {
+        &squashfs_xattr_user_handler,
+        &squashfs_xattr_trusted_handler,
+        &squashfs_xattr_security_handler,
+        NULL
+};
+