On Fri, May 18, 2012 at 11:55:21AM -0700, Linus Torvalds wrote:
> On Fri, May 18, 2012 at 11:45 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> >
> > It's actually not big. ?Completely untested minimal variant (without
> > touching ->d_revalidate()):
>
> Get rid of all the now unnecessary files stuff and error handling in
> proc_fd_instantiate() too (it's unnecessary - it only ends up being
> re-done in the revalidate function anyway), and I'll take it.
Umm... I'd rather do it other way - do that test *before* bothering
with allocating an inode. IOW, use it as early cutoff, with
tid_fd_revalidate() called in the end closing any races about
file getting closed while we'd been allocating an inode, etc.
IOW, how about this? Note that it's _still_ completely untested wrt
weird LSM stuff. I simply don't have tomoyo/apparmor/whatnot setups
to test on, so I'd rather see an ACK from the LSM people.
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1c8b280..e663a04 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1491,6 +1491,44 @@ static const struct inode_operations proc_pid_link_inode_operations = {
.setattr = proc_setattr,
};
+static int proc_fd_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
+{
+ struct inode *inode = dentry->d_inode;
+ struct files_struct *files;
+ struct task_struct *task;
+ struct file *file;
+ fmode_t mode = 0;
+
+ generic_fillattr(inode, stat);
+
+ rcu_read_lock();
+ task = pid_task(proc_pid(inode), PIDTYPE_PID);
+ files = task ? get_files_struct(task) : NULL;
+ file = files ? fcheck_files(files, PROC_I(inode)->fd) : NULL;
+ if (file)
+ mode = file->f_mode;
+ rcu_read_unlock();
+
+ if (files)
+ put_files_struct(files);
+ if (!file)
+ return -ENOENT;
+
+ if (mode & FMODE_READ)
+ stat->mode |= S_IRUSR | S_IXUSR;
+ if (mode & FMODE_WRITE)
+ stat->mode |= S_IWUSR | S_IXUSR;
+ stat->size = 64;
+ return 0;
+}
+
+static const struct inode_operations proc_pid_fd_inode_operations = {
+ .readlink = proc_pid_readlink,
+ .follow_link = proc_pid_follow_link,
+ .setattr = proc_setattr,
+ .getattr = proc_fd_getattr,
+};
+
/* building an inode */
@@ -1837,54 +1875,38 @@ static struct dentry *proc_fd_instantiate(struct inode *dir,
struct dentry *dentry, struct task_struct *task, const void *ptr)
{
unsigned fd = *(const unsigned *)ptr;
- struct file *file;
- struct files_struct *files;
+ struct file *file = NULL;
+ struct files_struct *files = get_files_struct(task);
struct inode *inode;
struct proc_inode *ei;
- struct dentry *error = ERR_PTR(-ENOENT);
+
+ if (files) {
+ rcu_read_lock();
+ file = fcheck_files(files, fd);
+ rcu_read_unlock();
+ put_files_struct(files);
+ }
+
+ if (!file)
+ return ERR_PTR(-ENOENT);
inode = proc_pid_make_inode(dir->i_sb, task);
if (!inode)
- goto out;
+ return ERR_PTR(-ENOMEM);
ei = PROC_I(inode);
ei->fd = fd;
- files = get_files_struct(task);
- if (!files)
- goto out_iput;
inode->i_mode = S_IFLNK;
-
- /*
- * We are not taking a ref to the file structure, so we must
- * hold ->file_lock.
- */
- spin_lock(&files->file_lock);
- file = fcheck_files(files, fd);
- if (!file)
- goto out_unlock;
- if (file->f_mode & FMODE_READ)
- inode->i_mode |= S_IRUSR | S_IXUSR;
- if (file->f_mode & FMODE_WRITE)
- inode->i_mode |= S_IWUSR | S_IXUSR;
- spin_unlock(&files->file_lock);
- put_files_struct(files);
-
- inode->i_op = &proc_pid_link_inode_operations;
- inode->i_size = 64;
+ inode->i_op = &proc_pid_fd_inode_operations;
ei->op.proc_get_link = proc_fd_link;
d_set_d_op(dentry, &tid_fd_dentry_operations);
d_add(dentry, inode);
- /* Close the race of the process dying before we return the dentry */
- if (tid_fd_revalidate(dentry, NULL))
- error = NULL;
-
- out:
- return error;
-out_unlock:
- spin_unlock(&files->file_lock);
- put_files_struct(files);
-out_iput:
- iput(inode);
- goto out;
+ /*
+ * Close the race of the process dying or file getting closed
+ * before we return the dentry
+ */
+ if (!tid_fd_revalidate(dentry, NULL))
+ return ERR_PTR(-ENOENT);
+ return NULL;
}
static struct dentry *proc_lookupfd_common(struct inode *dir,
--
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