vfs: Apply lockdep-based checking to rcu_dereference() uses
Paul E. McKenney [Tue, 23 Feb 2010 01:04:52 +0000 (17:04 -0800)]
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>

fs/file.c
fs/proc/array.c
fs/proc/base.c
include/linux/fdtable.h

index 87e1290..38039af 100644 (file)
--- 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);
        }
index 13b5d07..18e20fe 100644 (file)
@@ -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);
        }
index 58324c2..623e2ff 100644 (file)
@@ -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;
index a2ec74b..144412f 100644 (file)
@@ -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;
 }