fs: add file and path permissions helpers

Add two simple helpers to check permissions on a file and path
respectively and convert over some callers. It simplifies quite a few
codepaths and also reduces the churn in later patches quite a bit.
Christoph also correctly points out that this makes codepaths (e.g.
ioctls) way easier to follow that would otherwise have to do more
complex argument passing than necessary.

Link: https://lore.kernel.org/r/20210121131959.646623-4-christian.brauner@ubuntu.com
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/fs/init.c b/fs/init.c
index e9c320a..02723be 100644 (file)
--- a/fs/init.c
+++ b/fs/init.c
@@ -49,7 +49,7 @@ int __init init_chdir(const char *filename)
        error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
        if (error)
                return error;
-       error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
+       error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
        if (!error)
                set_fs_pwd(current->fs, &path);
        path_put(&path);
@@ -64,7 +64,7 @@ int __init init_chroot(const char *filename)
        error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
        if (error)
                return error;
-       error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
+       error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
        if (error)
                goto dput_and_out;
        error = -EPERM;
@@ -118,7 +118,7 @@ int __init init_eaccess(const char *filename)
        error = kern_path(filename, LOOKUP_FOLLOW, &path);
        if (error)
                return error;
-       error = inode_permission(d_inode(path.dentry), MAY_ACCESS);
+       error = path_permission(&path, MAY_ACCESS);
        path_put(&path);
        return error;
 }

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index dcab112..64cfc1a 100644 (file)
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -702,7 +702,7 @@ static int fanotify_find_path(int dfd, const char __user *filename,
        }
 
        /* you can only watch an inode if you have read permissions on it */
-       ret = inode_permission(path->dentry->d_inode, MAY_READ);
+       ret = path_permission(path, MAY_READ);
        if (ret) {
                path_put(path);
                goto out;

diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 59c1770..e1155d3 100644 (file)
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -352,7 +352,7 @@ static int inotify_find_inode(const char __user *dirname, struct path *path,
        if (error)
                return error;
        /* you can only watch an inode if you have read permissions on it */
-       error = inode_permission(path->dentry->d_inode, MAY_READ);
+       error = path_permission(path, MAY_READ);
        if (error) {
                path_put(path);
                return error;

diff --git a/fs/open.c b/fs/open.c
index 1e06e44..cd1efd2 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -492,7 +492,7 @@ retry:
        if (error)
                goto out;
 
-       error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
+       error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
        if (error)
                goto dput_and_out;
 
@@ -521,7 +521,7 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd)
        if (!d_can_lookup(f.file->f_path.dentry))
                goto out_putf;
 
-       error = inode_permission(file_inode(f.file), MAY_EXEC | MAY_CHDIR);
+       error = file_permission(f.file, MAY_EXEC | MAY_CHDIR);
        if (!error)
                set_fs_pwd(current->fs, &f.file->f_path);
 out_putf:
@@ -540,7 +540,7 @@ retry:
        if (error)
                goto out;
 
-       error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
+       error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
        if (error)
                goto dput_and_out;
 

diff --git a/fs/udf/file.c b/fs/udf/file.c
index ad8eefa..3671a40 100644 (file)
--- a/fs/udf/file.c
+++ b/fs/udf/file.c
@@ -183,7 +183,7 @@ long udf_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
        long old_block, new_block;
        int result;
 
-       if (inode_permission(inode, MAY_READ) != 0) {
+       if (file_permission(filp, MAY_READ) != 0) {
                udf_debug("no permission to access inode %lu\n", inode->i_ino);
                return -EPERM;
        }

diff --git a/fs/verity/enable.c b/fs/verity/enable.c
index f7e997a..77e159a 100644 (file)
--- a/fs/verity/enable.c
+++ b/fs/verity/enable.c
@@ -369,7 +369,7 @@ int fsverity_ioctl_enable(struct file *filp, const void __user *uarg)
         * has verity enabled, and to stabilize the data being hashed.
         */
 
-       err = inode_permission(inode, MAY_WRITE);
+       err = file_permission(filp, MAY_WRITE);
        if (err)
                return err;
 

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3165998..bcd1709 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2812,6 +2812,14 @@ static inline int bmap(struct inode *inode,  sector_t *block)
 extern int notify_change(struct dentry *, struct iattr *, struct inode **);
 extern int inode_permission(struct inode *, int);
 extern int generic_permission(struct inode *, int);
+static inline int file_permission(struct file *file, int mask)
+{
+       return inode_permission(file_inode(file), mask);
+}
+static inline int path_permission(const struct path *path, int mask)
+{
+       return inode_permission(d_inode(path->dentry), mask);
+}
 extern int __check_sticky(struct inode *dir, struct inode *inode);
 
 static inline bool execute_ok(struct inode *inode)

diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index dd4b7fd..8962f13 100644 (file)
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -507,7 +507,7 @@ static void *bpf_obj_do_get(const char __user *pathname,
                return ERR_PTR(ret);
 
        inode = d_backing_inode(path.dentry);
-       ret = inode_permission(inode, ACC_MODE(flags));
+       ret = path_permission(&path, ACC_MODE(flags));
        if (ret)
                goto out;
 

diff --git a/kernel/sys.c b/kernel/sys.c
index 51f00fe..138fb25 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1848,7 +1848,7 @@ static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
        if (!S_ISREG(inode->i_mode) || path_noexec(&exe.file->f_path))
                goto exit;
 
-       err = inode_permission(inode, MAY_EXEC);
+       err = file_permission(exe.file, MAY_EXEC);
        if (err)
                goto exit;
 

diff --git a/mm/madvise.c b/mm/madvise.c
index 6a66085..175c558 100644 (file)
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -540,7 +540,7 @@ static inline bool can_do_pageout(struct vm_area_struct *vma)
         * opens a side channel.
         */
        return inode_owner_or_capable(file_inode(vma->vm_file)) ||
-               inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0;
+              file_permission(vma->vm_file, MAY_WRITE) == 0;
 }
 
 static long madvise_pageout(struct vm_area_struct *vma,

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 605f671..cf9076f 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4899,7 +4899,7 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
 
        /* the process need read permission on control file */
        /* AV: shouldn't we check that it's been opened for read instead? */
-       ret = inode_permission(file_inode(cfile.file), MAY_READ);
+       ret = file_permission(cfile.file, MAY_READ);
        if (ret < 0)
                goto out_put_cfile;
 

diff --git a/mm/mincore.c b/mm/mincore.c
index 02db1a8..7bdb467 100644 (file)
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -167,7 +167,7 @@ static inline bool can_do_mincore(struct vm_area_struct *vma)
         * mappings, which opens a side channel.
         */
        return inode_owner_or_capable(file_inode(vma->vm_file)) ||
-               inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0;
+              file_permission(vma->vm_file, MAY_WRITE) == 0;
 }
 
 static const struct mm_walk_ops mincore_walk_ops = {

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 41c3303..18453d1 100644 (file)
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -936,7 +936,7 @@ static struct sock *unix_find_other(struct net *net,
                if (err)
                        goto fail;
                inode = d_backing_inode(path.dentry);
-               err = inode_permission(inode, MAY_WRITE);
+               err = path_permission(&path, MAY_WRITE);
                if (err)
                        goto put_fail;