[PATCH 1/2] proc: add and remove /proc entry create checks

[PATCH 1/2] proc: add and remove /proc entry create checks

[Alexey Dobriyan]

* remove proc_create(NULL, ...) check, let it oops

* warn about proc_create("", ...) and proc_create("very very long name", ...)
  proc code keeps length as u8, no 256+ name length possible

* warn about proc_create("123", ...)
  /proc/$PID and /proc/misc namespaces are separate things,
  but dumb module might create funky a-la $PID entry.

* remove post mortem strchr('/') check
  Triggering it implies either strchr() is buggy or memory corruption.
  It should be VFS check anyway.

In reality, none of these checks will ever trigger,
it is preparation for the next patch.

Based on patch from Al Viro.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 fs/proc/base.c     |    4 ++--
 fs/proc/fd.c       |    2 +-
 fs/proc/generic.c  |   30 +++++++++++++++---------------
 fs/proc/internal.h |    6 +++---
 4 files changed, 21 insertions(+), 21 deletions(-)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2785,7 +2785,7 @@ struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsign
 	unsigned tgid;
 	struct pid_namespace *ns;
 
-	tgid = name_to_int(dentry);
+	tgid = name_to_int(&dentry->d_name);
 	if (tgid == ~0U)
 		goto out;
 
@@ -3033,7 +3033,7 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry
 	if (!leader)
 		goto out_no_task;
 
-	tid = name_to_int(dentry);
+	tid = name_to_int(&dentry->d_name);
 	if (tid == ~0U)
 		goto out;
 
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -206,7 +206,7 @@ static struct dentry *proc_lookupfd_common(struct inode *dir,
 {
 	struct task_struct *task = get_proc_task(dir);
 	int result = -ENOENT;
-	unsigned fd = name_to_int(dentry);
+	unsigned fd = name_to_int(&dentry->d_name);
 
 	if (!task)
 		goto out_no_task;
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -330,28 +330,28 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
 					  nlink_t nlink)
 {
 	struct proc_dir_entry *ent = NULL;
-	const char *fn = name;
-	unsigned int len;
-
-	/* make sure name is valid */
-	if (!name || !strlen(name))
-		goto out;
+	const char *fn;
+	struct qstr qstr;
 
 	if (xlate_proc_name(name, parent, &fn) != 0)
 		goto out;
+	qstr.name = fn;
+	qstr.len = strlen(fn);
+	if (qstr.len == 0 || qstr.len >= 256) {
+		WARN(1, "name len %u\n", qstr.len);
+		return NULL;
+	}
+	if (*parent == &proc_root && name_to_int(&qstr) != ~0U) {
+		WARN(1, "create '/proc/%s' by hand\n", qstr.name);
+		return NULL;
+	}
 
-	/* At this point there must not be any '/' characters beyond *fn */
-	if (strchr(fn, '/'))
-		goto out;
-
-	len = strlen(fn);
-
-	ent = kzalloc(sizeof(struct proc_dir_entry) + len + 1, GFP_KERNEL);
+	ent = kzalloc(sizeof(struct proc_dir_entry) + qstr.len + 1, GFP_KERNEL);
 	if (!ent)
 		goto out;
 
-	memcpy(ent->name, fn, len + 1);
-	ent->namelen = len;
+	memcpy(ent->name, fn, qstr.len + 1);
+	ent->namelen = qstr.len;
 	ent->mode = mode;
 	ent->nlink = nlink;
 	atomic_set(&ent->count, 1);
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -112,10 +112,10 @@ static inline int task_dumpable(struct task_struct *task)
 	return 0;
 }
 
-static inline unsigned name_to_int(struct dentry *dentry)
+static inline unsigned name_to_int(const struct qstr *qstr)
 {
-	const char *name = dentry->d_name.name;
-	int len = dentry->d_name.len;
+	const char *name = qstr->name;
+	int len = qstr->len;
 	unsigned n = 0;
 
 	if (len > 1 && *name == '0')

[PATCH 2/2] proc: faster /proc/$PID lookup

[Alexey Dobriyan]

Currently lookup for /proc/$PID first goes through spinlock and
whole list of misc /proc entries only to confirm that, yes,
/proc/42 can not possibly match random proc entry.

List is is several dozens entries long (52 entries on my setup).

None of this is necessary.

Try to convert dentry name to integer first.
If it works, it must be /proc/$PID.
If it doesn't, it must be random proc entry.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 fs/proc/base.c |    2 +-
 fs/proc/root.c |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2780,7 +2780,7 @@ out:
 
 struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)
 {
-	int result = 0;
+	int result = -ENOENT;
 	struct task_struct *task;
 	unsigned tgid;
 	struct pid_namespace *ns;
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -199,10 +199,10 @@ static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct
 
 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
 {
-	if (!proc_lookup(dir, dentry, flags))
+	if (!proc_pid_lookup(dir, dentry, flags))
 		return NULL;
 	
-	return proc_pid_lookup(dir, dentry, flags);
+	return proc_lookup(dir, dentry, flags);
 }
 
 static int proc_root_readdir(struct file *file, struct dir_context *ctx)

Re: [PATCH 2/2] proc: faster /proc/$PID lookup

[Alexey Dobriyan]

On Wed, Jul 09, 2014 at 12:45:57AM +0300, Alexey Dobriyan wrote:
> Currently lookup for /proc/$PID first goes through spinlock and
> whole list of misc /proc entries only to confirm that, yes,
> /proc/42 can not possibly match random proc entry.
> 
> List is is several dozens entries long (52 entries on my setup).
> 
> None of this is necessary.
> 
> Try to convert dentry name to integer first.
> If it works, it must be /proc/$PID.
> If it doesn't, it must be random proc entry.

Recycled from Al Viro's patch as well!