[PATCH] file: modify struct fown_struct to use a struct pid

File handles can be requested to send sigio and sigurg to processes.  By
tracking the destination processes using struct pid instead of pid_t we make
the interface safe from all potential pid wrap around problems.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 49 insertions, 28 deletions

diff --git a/fs/fcntl.c b/fs/fcntl.c
index d35cbc6bc112..e7c66a1bf831 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -250,19 +250,22 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
         return error;
 }
 
-static void f_modown(struct file *filp, unsigned long pid,
+static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
                      uid_t uid, uid_t euid, int force)
 {
         write_lock_irq(&filp->f_owner.lock);
         if (force || !filp->f_owner.pid) {
-                filp->f_owner.pid = pid;
+                put_pid(filp->f_owner.pid);
+                filp->f_owner.pid = get_pid(pid);
+                filp->f_owner.pid_type = type;
                 filp->f_owner.uid = uid;
                 filp->f_owner.euid = euid;
         }
         write_unlock_irq(&filp->f_owner.lock);
 }
 
-int f_setown(struct file *filp, unsigned long arg, int force)
+int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
+                int force)
 {
         int err;
         
@@ -270,15 +273,42 @@ int f_setown(struct file *filp, unsigned long arg, int force)
         if (err)
                 return err;
 
-        f_modown(filp, arg, current->uid, current->euid, force);
+        f_modown(filp, pid, type, current->uid, current->euid, force);
         return 0;
 }
+EXPORT_SYMBOL(__f_setown);
 
+int f_setown(struct file *filp, unsigned long arg, int force)
+{
+        enum pid_type type;
+        struct pid *pid;
+        int who = arg;
+        int result;
+        type = PIDTYPE_PID;
+        if (who < 0) {
+                type = PIDTYPE_PGID;
+                who = -who;
+        }
+        rcu_read_lock();
+        pid = find_pid(who);
+        result = __f_setown(filp, pid, type, force);
+        rcu_read_unlock();
+        return result;
+}
 EXPORT_SYMBOL(f_setown);
 
 void f_delown(struct file *filp)
 {
-        f_modown(filp, 0, 0, 0, 1);
+        f_modown(filp, NULL, PIDTYPE_PID, 0, 0, 1);
+}
+
+pid_t f_getown(struct file *filp)
+{
+        pid_t pid;
+        pid = pid_nr(filp->f_owner.pid);
+        if (filp->f_owner.pid_type == PIDTYPE_PGID)
+                pid = -pid;
+        return pid;
 }
 
 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
@@ -319,7 +349,7 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
                  * current syscall conventions, the only way
                  * to fix this will be in libc.
                  */
-                err = filp->f_owner.pid;
+                err = f_getown(filp);
                 force_successful_syscall_return();
                 break;
         case F_SETOWN:
@@ -470,24 +500,19 @@ static void send_sigio_to_task(struct task_struct *p,
 void send_sigio(struct fown_struct *fown, int fd, int band)
 {
         struct task_struct *p;
-        int pid;
+        enum pid_type type;
+        struct pid *pid;
         
         read_lock(&fown->lock);
+        type = fown->pid_type;
         pid = fown->pid;
         if (!pid)
                 goto out_unlock_fown;
         
         read_lock(&tasklist_lock);
-        if (pid > 0) {
-                p = find_task_by_pid(pid);
-                if (p) {
-                        send_sigio_to_task(p, fown, fd, band);
-                }
-        } else {
-                do_each_task_pid(-pid, PIDTYPE_PGID, p) {
-                        send_sigio_to_task(p, fown, fd, band);
-                } while_each_task_pid(-pid, PIDTYPE_PGID, p);
-        }
+        do_each_pid_task(pid, type, p) {
+                send_sigio_to_task(p, fown, fd, band);
+        } while_each_pid_task(pid, type, p);
         read_unlock(&tasklist_lock);
  out_unlock_fown:
         read_unlock(&fown->lock);
@@ -503,9 +528,12 @@ static void send_sigurg_to_task(struct task_struct *p,
 int send_sigurg(struct fown_struct *fown)
 {
         struct task_struct *p;
-        int pid, ret = 0;
+        enum pid_type type;
+        struct pid *pid;
+        int ret = 0;
         
         read_lock(&fown->lock);
+        type = fown->pid_type;
         pid = fown->pid;
         if (!pid)
                 goto out_unlock_fown;
@@ -513,16 +541,9 @@ int send_sigurg(struct fown_struct *fown)
         ret = 1;
         
         read_lock(&tasklist_lock);
-        if (pid > 0) {
-                p = find_task_by_pid(pid);
-                if (p) {
-                        send_sigurg_to_task(p, fown);
-                }
-        } else {
-                do_each_task_pid(-pid, PIDTYPE_PGID, p) {
-                        send_sigurg_to_task(p, fown);
-                } while_each_task_pid(-pid, PIDTYPE_PGID, p);
-        }
+        do_each_pid_task(pid, type, p) {
+                send_sigurg_to_task(p, fown);
+        } while_each_pid_task(pid, type, p);
         read_unlock(&tasklist_lock);
  out_unlock_fown:
         read_unlock(&fown->lock);