anonfd: Allow making anon files read-only

It seems a couple places such as arch/ia64/kernel/perfmon.c and drivers/infiniband/core/uverbs_main.c could use anon_inode_getfile() instead of a private pseudo-fs + alloc_file(), if only there were a way to get a read-only file. So provide this by having anon_inode_getfile() create a read-only file if we pass O_RDONLY in flags. Signed-off-by: Roland Dreier <rolandd@cisco.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

anonfd: Allow making anon files read-only
It seems a couple places such as arch/ia64/kernel/perfmon.c and drivers/infiniband/core/uverbs_main.c could use anon_inode_getfile() instead of a private pseudo-fs + alloc_file(), if only there were a way to get a read-only file. So provide this by having anon_inode_getfile() create a read-only file if we pass O_RDONLY in flags. Signed-off-by: Roland Dreier <rolandd@cisco.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Roland Dreier · Al Viro
1 parent ed2617585f
Showing 7 changed files with 17 additions and 9 deletions Side-by-side Diff
fs/anon_inodes.c
fs/eventfd.c
fs/eventpoll.c
fs/signalfd.c
fs/timerfd.c
kernel/perf_event.c
virt/kvm/kvm_main.c
@@ -89,11 +89,19 @@
 	struct qstr this;
 	struct path path;
 	struct file *file;
+	fmode_t mode;
 	int error;
  
 	if (IS_ERR(anon_inode_inode))
 		return ERR_PTR(-ENODEV);
  
+	switch (flags & O_ACCMODE) {
+	case O_RDONLY: mode = FMODE_READ;		break;
+	case O_WRONLY: mode = FMODE_WRITE;		break;
+	case O_RDWR:   mode = FMODE_READ | FMODE_WRITE;	break;
+	default:       return ERR_PTR(-EINVAL);
+	}
+
 	if (fops->owner && !try_module_get(fops->owner))
 		return ERR_PTR(-ENOENT);
  
  
@@ -121,13 +129,13 @@
 	d_instantiate(path.dentry, anon_inode_inode);
  
 	error = -ENFILE;
-	file = alloc_file(&path, FMODE_READ | FMODE_WRITE, fops);
+	file = alloc_file(&path, mode, fops);
 	if (!file)
 		goto err_dput;
 	file->f_mapping = anon_inode_inode->i_mapping;
  
 	file->f_pos = 0;
-	file->f_flags = O_RDWR | (flags & O_NONBLOCK);
+	file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
 	file->f_version = 0;
 	file->private_data = priv;
  
@@ -339,7 +339,7 @@
 	ctx->flags = flags;
  
 	file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,
-				  flags & EFD_SHARED_FCNTL_FLAGS);
+				  O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
 	if (IS_ERR(file))
 		eventfd_free_ctx(ctx);
  
@@ -1206,7 +1206,7 @@
 	 * a file structure and a free file descriptor.
 	 */
 	error = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep,
-				 flags & O_CLOEXEC);
+				 O_RDWR | (flags & O_CLOEXEC));
 	if (error < 0)
 		ep_free(ep);
  
@@ -236,7 +236,7 @@
 		 * anon_inode_getfd() will install the fd.
 		 */
 		ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
-				       flags & (O_CLOEXEC | O_NONBLOCK));
+				       O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
 		if (ufd < 0)
 			kfree(ctx);
 	} else {
@@ -200,7 +200,7 @@
 	hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
  
 	ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
-			       flags & TFD_SHARED_FCNTL_FLAGS);
+			       O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
 	if (ufd < 0)
 		kfree(ctx);
  
@@ -4724,7 +4724,7 @@
 	if (IS_ERR(event))
 		goto err_put_context;
  
-	err = anon_inode_getfd("[perf_event]", &perf_fops, event, 0);
+	err = anon_inode_getfd("[perf_event]", &perf_fops, event, O_RDWR);
 	if (err < 0)
 		goto err_free_put_context;
  
@@ -1177,7 +1177,7 @@
  */
 static int create_vcpu_fd(struct kvm_vcpu *vcpu)
 {
-	return anon_inode_getfd("kvm-vcpu", &kvm_vcpu_fops, vcpu, 0);
+	return anon_inode_getfd("kvm-vcpu", &kvm_vcpu_fops, vcpu, O_RDWR);
 }
  
 /*
@@ -1638,7 +1638,7 @@
 	kvm = kvm_create_vm();
 	if (IS_ERR(kvm))
 		return PTR_ERR(kvm);
-	fd = anon_inode_getfd("kvm-vm", &kvm_vm_fops, kvm, 0);
+	fd = anon_inode_getfd("kvm-vm", &kvm_vm_fops, kvm, O_RDWR);
 	if (fd < 0)
 		kvm_put_kvm(kvm);
...	...	@@ -89,11 +89,19 @@
89	89	struct qstr this;
90	90	struct path path;
91	91	struct file *file;
	92	+ fmode_t mode;
92	93	int error;
93	94
94	95	if (IS_ERR(anon_inode_inode))
95	96	return ERR_PTR(-ENODEV);
96	97
	98	+ switch (flags & O_ACCMODE) {
	99	+ case O_RDONLY: mode = FMODE_READ; break;
	100	+ case O_WRONLY: mode = FMODE_WRITE; break;
	101	+ case O_RDWR: mode = FMODE_READ \| FMODE_WRITE; break;
	102	+ default: return ERR_PTR(-EINVAL);
	103	+ }
	104	+
97	105	if (fops->owner && !try_module_get(fops->owner))
98	106	return ERR_PTR(-ENOENT);
99	107
100	108
...	...	@@ -121,13 +129,13 @@
121	129	d_instantiate(path.dentry, anon_inode_inode);
122	130
123	131	error = -ENFILE;
124		- file = alloc_file(&path, FMODE_READ \| FMODE_WRITE, fops);
	132	+ file = alloc_file(&path, mode, fops);
125	133	if (!file)
126	134	goto err_dput;
127	135	file->f_mapping = anon_inode_inode->i_mapping;
128	136
129	137	file->f_pos = 0;
130		- file->f_flags = O_RDWR \| (flags & O_NONBLOCK);
	138	+ file->f_flags = flags & (O_ACCMODE \| O_NONBLOCK);
131	139	file->f_version = 0;
132	140	file->private_data = priv;
133	141
...	...	@@ -339,7 +339,7 @@
339	339	ctx->flags = flags;
340	340
341	341	file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,
342		- flags & EFD_SHARED_FCNTL_FLAGS);
	342	+ O_RDWR \| (flags & EFD_SHARED_FCNTL_FLAGS));
343	343	if (IS_ERR(file))
344	344	eventfd_free_ctx(ctx);
345	345
...	...	@@ -1206,7 +1206,7 @@
1206	1206	* a file structure and a free file descriptor.
1207	1207	*/
1208	1208	error = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep,
1209		- flags & O_CLOEXEC);
	1209	+ O_RDWR \| (flags & O_CLOEXEC));
1210	1210	if (error < 0)
1211	1211	ep_free(ep);
1212	1212
...	...	@@ -236,7 +236,7 @@
236	236	* anon_inode_getfd() will install the fd.
237	237	*/
238	238	ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
239		- flags & (O_CLOEXEC \| O_NONBLOCK));
	239	+ O_RDWR \| (flags & (O_CLOEXEC \| O_NONBLOCK)));
240	240	if (ufd < 0)
241	241	kfree(ctx);
242	242	} else {
...	...	@@ -200,7 +200,7 @@
200	200	hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
201	201
202	202	ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
203		- flags & TFD_SHARED_FCNTL_FLAGS);
	203	+ O_RDWR \| (flags & TFD_SHARED_FCNTL_FLAGS));
204	204	if (ufd < 0)
205	205	kfree(ctx);
206	206
...	...	@@ -4724,7 +4724,7 @@
4724	4724	if (IS_ERR(event))
4725	4725	goto err_put_context;
4726	4726
4727		- err = anon_inode_getfd("[perf_event]", &perf_fops, event, 0);
	4727	+ err = anon_inode_getfd("[perf_event]", &perf_fops, event, O_RDWR);
4728	4728	if (err < 0)
4729	4729	goto err_free_put_context;
4730	4730
...	...	@@ -1177,7 +1177,7 @@
1177	1177	*/
1178	1178	static int create_vcpu_fd(struct kvm_vcpu *vcpu)
1179	1179	{
1180		- return anon_inode_getfd("kvm-vcpu", &kvm_vcpu_fops, vcpu, 0);
	1180	+ return anon_inode_getfd("kvm-vcpu", &kvm_vcpu_fops, vcpu, O_RDWR);
1181	1181	}
1182	1182
1183	1183	/*
...	...	@@ -1638,7 +1638,7 @@
1638	1638	kvm = kvm_create_vm();
1639	1639	if (IS_ERR(kvm))
1640	1640	return PTR_ERR(kvm);
1641		- fd = anon_inode_getfd("kvm-vm", &kvm_vm_fops, kvm, 0);
	1641	+ fd = anon_inode_getfd("kvm-vm", &kvm_vm_fops, kvm, O_RDWR);
1642	1642	if (fd < 0)
1643	1643	kvm_put_kvm(kvm);
1644	1644