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pramfs: symlink operations

PATCH In review Marco Stornelli 2 participants 3 messages Sep 7, 2013 VFS

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Marco Stornelli

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#0 lore raw

PATCH 12/19 pramfs: symlink operations

Add symlink operations.

Signed-off-by Marco Stornelli <[email protected]>
---
 fs/pramfs/symlink.c |   76 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 76 insertions(+), 0 deletions(-)
 create mode 100644 fs/pramfs/symlink.c
fs/pramfs/symlink.c new file +76 -0
new file mode 100644
index 0000000..0d5213f
@@ -0,0 +1,76 @@
+/*
+ * BRIEF DESCRIPTION
+ *
+ * Symlink operations
+ *
+ * Copyright 2009-2011 Marco Stornelli <[email protected]>
+ * Copyright 2003 Sony Corporation
+ * Copyright 2003 Matsushita Electric Industrial Co., Ltd.
+ * 2003-2004 (c) MontaVista Software, Inc. , Steve Longerbeam
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/fs.h>
+#include "pram.h"
+#include "xattr.h"
+
+int pram_block_symlink(struct inode *inode, const char *symname, int len)
+{
+	struct super_block *sb = inode->i_sb;
+	u64 block;
+	char *blockp;
+	int err;
+
+	err = pram_alloc_blocks(inode, 0, 1);
+	if (err)
+		return err;
+
+	block = pram_find_data_block(inode, 0);
+	blockp = pram_get_block(sb, block);
+
+	pram_memunlock_block(sb, blockp);
+	memcpy(blockp, symname, len);
+	blockp[len] = '\0';
+	pram_memlock_block(sb, blockp);
+	return 0;
+}
+
+static int pram_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+	struct inode *inode = dentry->d_inode;
+	struct super_block *sb = inode->i_sb;
+	u64 block;
+	char *blockp;
+
+	block = pram_find_data_block(inode, 0);
+	blockp = pram_get_block(sb, block);
+	return vfs_readlink(dentry, buffer, buflen, blockp);
+}
+
+static void *pram_follow_link(struct dentry *dentry, struct nameidata *nd)
+{
+	struct inode *inode = dentry->d_inode;
+	struct super_block *sb = inode->i_sb;
+	off_t block;
+	int status;
+	char *blockp;
+
+	block = pram_find_data_block(inode, 0);
+	blockp = pram_get_block(sb, block);
+	status = vfs_follow_link(nd, blockp);
+	return ERR_PTR(status);
+}
+
+const struct inode_operations pram_symlink_inode_operations = {
+	.readlink	= pram_readlink,
+	.follow_link	= pram_follow_link,
+	.setattr	= pram_notify_change,
+#ifdef CONFIG_PRAMFS_XATTR
+	.setxattr	= generic_setxattr,
+	.getxattr	= generic_getxattr,
+	.listxattr	= pram_listxattr,
+	.removexattr	= generic_removexattr,
+#endif
+};
Signature · 1 line
1.7.3.4
maintainer
#1 lore raw
Quoted 15 lines · Marco Stornelli
fs/pramfs/symlink.c new file +14 -0
+static int pram_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+	struct inode *inode = dentry->d_inode;
+	struct super_block *sb = inode->i_sb;
+	u64 block;
+	char *blockp;
+
+	block = pram_find_data_block(inode, 0);
+	blockp = pram_get_block(sb, block);
+	return vfs_readlink(dentry, buffer, buflen, blockp);
+}
 
+static void *pram_follow_link(struct dentry *dentry, struct nameidata *nd)
+{
+	struct inode *inode = dentry->d_inode;

fs/pramfs/symlink.c line 64

Quoted 10 lines
fs/pramfs/symlink.c new file +10 -0
+	struct super_block *sb = inode->i_sb;
+	off_t block;
+	int status;
+	char *blockp;
+
+	block = pram_find_data_block(inode, 0);
+	blockp = pram_get_block(sb, block);
+	status = vfs_follow_link(nd, blockp);
+	return ERR_PTR(status);
+}

Just nd_set_link(nd, blockp) instead of that vfs_follow_link() and be done with that; that way you can use generic_readlink() instead of pram_readlink() *and* get lower stack footprint on traversing them.

BTW, where's the error checking? pram_get_block()/pram_find_data_block() seem to assume that fs image isn't corrupted and if it is... that code will happily dereference any address. At least range checks of some sort in pram_get_block() (and checking if it has failed) would be a good idea...

author
#2 lore raw

Il 07/09/2013 16:41, Al Viro ha scritto:

Quoted 22 lines · Marco Stornelli
Quoted 21 lines
fs/pramfs/symlink.c new file +20 -0
+static int pram_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+	struct inode *inode = dentry->d_inode;
+	struct super_block *sb = inode->i_sb;
+	u64 block;
+	char *blockp;
+
+	block = pram_find_data_block(inode, 0);
+	blockp = pram_get_block(sb, block);
+	return vfs_readlink(dentry, buffer, buflen, blockp);
+}
 
+static void *pram_follow_link(struct dentry *dentry, struct nameidata *nd)
+{
+	struct inode *inode = dentry->d_inode;
+	struct super_block *sb = inode->i_sb;
+	off_t block;
+	int status;
+	char *blockp;
+
+	block = pram_find_data_block(inode, 0);
Quoted 10 lines

fs/pramfs/symlink.c line 64

Quoted 4 lines
fs/pramfs/symlink.c new file +4 -0
+	blockp = pram_get_block(sb, block);
+	status = vfs_follow_link(nd, blockp);
+	return ERR_PTR(status);
+}

Just nd_set_link(nd, blockp) instead of that vfs_follow_link() and be done with that; that way you can use generic_readlink() instead of pram_readlink() *and* get lower stack footprint on traversing them.

Yep, you're right (as usual :))

Marco