[PATCH] add a file_permission helper

A few more callers of permission() just want to check for a different access
pattern on an already open file.  This patch adds a wrapper for permission()
that takes a file in preparation of per-mount read-only support and to clean
up the callers a little.  The helper is not intended for new code, everything
without the interface set in stone should use vfs_permission()

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

8 files changed, 47 insertions, 21 deletions

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index dd1935d55424..28002de783b6 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3776,8 +3776,7 @@ static int floppy_open(struct inode *inode, struct file *filp)
         /* Allow ioctls if we have write-permissions even if read-only open.
          * Needed so that programs such as fdrawcmd still can work on write
          * protected disks */
-        if (filp->f_mode & 2
-            || permission(filp->f_dentry->d_inode, 2, NULL) == 0)
+        if ((filp->f_mode & FMODE_WRITE) || !file_permission(filp, MAY_WRITE))
                 filp->private_data = (void *)8;
 
         if (UFDCS->rawcmd == 1)
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 8ae0db6cd69c..2568eb41cb3a 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -150,7 +150,7 @@ static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 
                 /* if the binary is not readable than enforce mm->dumpable=0
                    regardless of the interpreter's permissions */
-                if (permission(bprm->file->f_dentry->d_inode, MAY_READ, NULL))
+                if (file_permission(bprm->file, MAY_READ))
                         bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
 
                 allow_write_access(bprm->file);
diff --git a/fs/exec.c b/fs/exec.c
index 7bbb781b9ac6..c466fec5de20 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -896,7 +896,7 @@ int flush_old_exec(struct linux_binprm * bprm)
         flush_thread();
 
         if (bprm->e_uid != current->euid || bprm->e_gid != current->egid || 
-            permission(bprm->file->f_dentry->d_inode,MAY_READ, NULL) ||
+            file_permission(bprm->file, MAY_READ) ||
             (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
                 suid_keys(current);
                 current->mm->dumpable = suid_dumpable;
diff --git a/fs/namei.c b/fs/namei.c
index 25e4ab4ce8b7..b69f6ebadb95 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -271,6 +271,23 @@ int vfs_permission(struct nameidata *nd, int mask)
         return permission(nd->dentry->d_inode, mask, nd);
 }
 
+/**
+ * file_permission  -  check for additional access rights to a given file
+ * @file:       file to check access rights for
+ * @mask:       right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ *
+ * Used to check for read/write/execute permissions on an already opened
+ * file.
+ *
+ * Note:
+ *      Do not use this function in new code.  All access checks should
+ *      be done using vfs_permission().
+ */
+int file_permission(struct file *file, int mask)
+{
+        return permission(file->f_dentry->d_inode, mask, NULL);
+}
+
 /*
  * get_write_access() gets write permission for a file.
  * put_write_access() releases this write permission.
@@ -2551,6 +2568,7 @@ EXPORT_SYMBOL(path_release);
 EXPORT_SYMBOL(path_walk);
 EXPORT_SYMBOL(permission);
 EXPORT_SYMBOL(vfs_permission);
+EXPORT_SYMBOL(file_permission);
 EXPORT_SYMBOL(unlock_rename);
 EXPORT_SYMBOL(vfs_create);
 EXPORT_SYMBOL(vfs_follow_link);
diff --git a/fs/ncpfs/ioctl.c b/fs/ncpfs/ioctl.c
index 88df79356a1f..fd3efdca5ae3 100644
--- a/fs/ncpfs/ioctl.c
+++ b/fs/ncpfs/ioctl.c
@@ -30,11 +30,13 @@
 #define NCP_PACKET_SIZE_INTERNAL 65536
 
 static int
-ncp_get_fs_info(struct ncp_server* server, struct inode* inode, struct ncp_fs_info __user *arg)
+ncp_get_fs_info(struct ncp_server * server, struct file *file,
+                struct ncp_fs_info __user *arg)
 {
+        struct inode *inode = file->f_dentry->d_inode;
         struct ncp_fs_info info;
 
-        if ((permission(inode, MAY_WRITE, NULL) != 0)
+        if ((file_permission(file, MAY_WRITE) != 0)
             && (current->uid != server->m.mounted_uid)) {
                 return -EACCES;
         }
@@ -58,11 +60,13 @@ ncp_get_fs_info(struct ncp_server* server, struct inode* inode, struct ncp_fs_in
 }
 
 static int
-ncp_get_fs_info_v2(struct ncp_server* server, struct inode* inode, struct ncp_fs_info_v2 __user * arg)
+ncp_get_fs_info_v2(struct ncp_server * server, struct file *file,
+                   struct ncp_fs_info_v2 __user * arg)
 {
+        struct inode *inode = file->f_dentry->d_inode;
         struct ncp_fs_info_v2 info2;
 
-        if ((permission(inode, MAY_WRITE, NULL) != 0)
+        if ((file_permission(file, MAY_WRITE) != 0)
             && (current->uid != server->m.mounted_uid)) {
                 return -EACCES;
         }
@@ -190,7 +194,7 @@ int ncp_ioctl(struct inode *inode, struct file *filp,
         switch (cmd) {
         case NCP_IOC_NCPREQUEST:
 
-                if ((permission(inode, MAY_WRITE, NULL) != 0)
+                if ((file_permission(filp, MAY_WRITE) != 0)
                     && (current->uid != server->m.mounted_uid)) {
                         return -EACCES;
                 }
@@ -245,16 +249,16 @@ int ncp_ioctl(struct inode *inode, struct file *filp,
                 return ncp_conn_logged_in(inode->i_sb);
 
         case NCP_IOC_GET_FS_INFO:
-                return ncp_get_fs_info(server, inode, argp);
+                return ncp_get_fs_info(server, filp, argp);
 
         case NCP_IOC_GET_FS_INFO_V2:
-                return ncp_get_fs_info_v2(server, inode, argp);
+                return ncp_get_fs_info_v2(server, filp, argp);
 
         case NCP_IOC_GETMOUNTUID2:
                 {
                         unsigned long tmp = server->m.mounted_uid;
 
-                        if (   (permission(inode, MAY_READ, NULL) != 0)
+                        if ((file_permission(filp, MAY_READ) != 0)
                             && (current->uid != server->m.mounted_uid))
                         {
                                 return -EACCES;
@@ -268,7 +272,7 @@ int ncp_ioctl(struct inode *inode, struct file *filp,
                 {
                         struct ncp_setroot_ioctl sr;
 
-                        if (   (permission(inode, MAY_READ, NULL) != 0)
+                        if ((file_permission(filp, MAY_READ) != 0)
                             && (current->uid != server->m.mounted_uid))
                         {
                                 return -EACCES;
@@ -343,7 +347,7 @@ int ncp_ioctl(struct inode *inode, struct file *filp,
 
 #ifdef CONFIG_NCPFS_PACKET_SIGNING      
         case NCP_IOC_SIGN_INIT:
-                if ((permission(inode, MAY_WRITE, NULL) != 0)
+                if ((file_permission(filp, MAY_WRITE) != 0)
                     && (current->uid != server->m.mounted_uid))
                 {
                         return -EACCES;
@@ -366,7 +370,7 @@ int ncp_ioctl(struct inode *inode, struct file *filp,
                 return 0;               
                 
         case NCP_IOC_SIGN_WANTED:
-                if (   (permission(inode, MAY_READ, NULL) != 0)
+                if ((file_permission(filp, MAY_READ) != 0)
                     && (current->uid != server->m.mounted_uid))
                 {
                         return -EACCES;
@@ -379,7 +383,7 @@ int ncp_ioctl(struct inode *inode, struct file *filp,
                 {
                         int newstate;
 
-                        if (   (permission(inode, MAY_WRITE, NULL) != 0)
+                        if ((file_permission(filp, MAY_WRITE) != 0)
                             && (current->uid != server->m.mounted_uid))
                         {
                                 return -EACCES;
@@ -400,7 +404,7 @@ int ncp_ioctl(struct inode *inode, struct file *filp,
 
 #ifdef CONFIG_NCPFS_IOCTL_LOCKING
         case NCP_IOC_LOCKUNLOCK:
-                if (   (permission(inode, MAY_WRITE, NULL) != 0)
+                if ((file_permission(filp, MAY_WRITE) != 0)
                     && (current->uid != server->m.mounted_uid))
                 {
                         return -EACCES;
@@ -605,7 +609,7 @@ outrel:
 #endif /* CONFIG_NCPFS_NLS */
 
         case NCP_IOC_SETDENTRYTTL:
-                if ((permission(inode, MAY_WRITE, NULL) != 0) &&
+                if ((file_permission(filp, MAY_WRITE) != 0) &&
                                  (current->uid != server->m.mounted_uid))
                         return -EACCES;
                 {
@@ -635,7 +639,7 @@ outrel:
            so we have this out of switch */
         if (cmd == NCP_IOC_GETMOUNTUID) {
                 __kernel_uid_t uid = 0;
-                if ((permission(inode, MAY_READ, NULL) != 0)
+                if ((file_permission(filp, MAY_READ) != 0)
                     && (current->uid != server->m.mounted_uid)) {
                         return -EACCES;
                 }
diff --git a/fs/open.c b/fs/open.c
index baffc084580d..f53a5b9ffb7d 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -563,7 +563,7 @@ asmlinkage long sys_fchdir(unsigned int fd)
         if (!S_ISDIR(inode->i_mode))
                 goto out_putf;
 
-        error = permission(inode, MAY_EXEC, NULL);
+        error = file_permission(file, MAY_EXEC);
         if (!error)
                 set_fs_pwd(current->fs, mnt, dentry);
 out_putf:
diff --git a/fs/udf/file.c b/fs/udf/file.c
index bb40d63f328f..01f520c71dc1 100644
--- a/fs/udf/file.c
+++ b/fs/udf/file.c
@@ -186,7 +186,7 @@ int udf_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
 {
         int result = -EINVAL;
 
-        if ( permission(inode, MAY_READ, NULL) != 0 )
+        if ( file_permission(filp, MAY_READ) != 0 )
         {
                 udf_debug("no permission to access inode %lu\n",
                                                 inode->i_ino);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c3b8c1dc7cdf..cc35b6ac778d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -890,6 +890,11 @@ extern int vfs_rename(struct inode *, struct dentry *, struct inode *, struct de
 extern void dentry_unhash(struct dentry *dentry);
 
 /*
+ * VFS file helper functions.
+ */
+extern int file_permission(struct file *, int);
+
+/*
  * File types
  *
  * NOTE! These match bits 12..15 of stat.st_mode