vfs: Apply lockdep-based checking to rcu_dereference() uses

Add lockdep-ified RCU primitives to alloc_fd(), files_fdtable()
and fcheck_files().

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
LKML-Reference: <1266887105-1528-8-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

4 files changed, 14 insertions, 4 deletions

diff --git a/fs/file.c b/fs/file.c
index 87e129030ab1..38039af67663 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -478,7 +478,7 @@ repeat:
         error = fd;
 #if 1
         /* Sanity check */
-        if (rcu_dereference(fdt->fd[fd]) != NULL) {
+        if (rcu_dereference_raw(fdt->fd[fd]) != NULL) {
                 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
                 rcu_assign_pointer(fdt->fd[fd], NULL);
         }
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 13b5d0708175..18e20feee251 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -270,7 +270,9 @@ static inline void task_sig(struct seq_file *m, struct task_struct *p)
                 blocked = p->blocked;
                 collect_sigign_sigcatch(p, &ignored, &caught);
                 num_threads = atomic_read(&p->signal->count);
+                rcu_read_lock();  /* FIXME: is this correct? */
                 qsize = atomic_read(&__task_cred(p)->user->sigpending);
+                rcu_read_unlock();
                 qlim = p->signal->rlim[RLIMIT_SIGPENDING].rlim_cur;
                 unlock_task_sighand(p, &flags);
         }
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 58324c299165..623e2ffb5d2b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1095,8 +1095,12 @@ static ssize_t proc_loginuid_write(struct file * file, const char __user * buf,
         if (!capable(CAP_AUDIT_CONTROL))
                 return -EPERM;
 
-        if (current != pid_task(proc_pid(inode), PIDTYPE_PID))
+        rcu_read_lock();
+        if (current != pid_task(proc_pid(inode), PIDTYPE_PID)) {
+                rcu_read_unlock();
                 return -EPERM;
+        }
+        rcu_read_unlock();
 
         if (count >= PAGE_SIZE)
                 count = PAGE_SIZE - 1;
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index a2ec74bc4812..144412ffaced 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -57,7 +57,11 @@ struct files_struct {
         struct file * fd_array[NR_OPEN_DEFAULT];
 };
 
-#define files_fdtable(files) (rcu_dereference((files)->fdt))
+#define files_fdtable(files) \
+        (rcu_dereference_check((files)->fdt, \
+                               rcu_read_lock_held() || \
+                               lockdep_is_held(&(files)->file_lock) || \
+                               atomic_read(&files->count) == 1))
 
 struct file_operations;
 struct vfsmount;
@@ -78,7 +82,7 @@ static inline struct file * fcheck_files(struct files_struct *files, unsigned in
         struct fdtable *fdt = files_fdtable(files);
 
         if (fd < fdt->max_fds)
-                file = rcu_dereference(fdt->fd[fd]);
+                file = rcu_dereference_check(fdt->fd[fd], rcu_read_lock_held() || lockdep_is_held(&files->file_lock) || atomic_read(&files->count) == 1);
         return file;
 }