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>

1 files changed, 5 insertions, 1 deletions

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;