[PATCH] file: modify struct fown_struct to use a struct pid
Eric W. Biederman [Mon, 2 Oct 2006 09:17:15 +0000 (02:17 -0700)]
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>

drivers/net/tun.c
fs/dnotify.c
fs/fcntl.c
fs/file_table.c
fs/locks.c
include/linux/fs.h
kernel/futex.c
net/socket.c

index bc0face..151a2e1 100644 (file)
@@ -697,7 +697,7 @@ static int tun_chr_fasync(int fd, struct file *file, int on)
                return ret;
 
        if (on) {
-               ret = f_setown(file, current->pid, 0);
+               ret = __f_setown(file, task_pid(current), PIDTYPE_PID, 0);
                if (ret)
                        return ret;
                tun->flags |= TUN_FASYNC;
index f932591..2b0442d 100644 (file)
@@ -92,7 +92,7 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
                prev = &odn->dn_next;
        }
 
-       error = f_setown(filp, current->pid, 0);
+       error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
        if (error)
                goto out_free;
 
index d35cbc6..e7c66a1 100644 (file)
@@ -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);
index bc35a40..24f25a0 100644 (file)
@@ -174,6 +174,7 @@ void fastcall __fput(struct file *file)
        fops_put(file->f_op);
        if (file->f_mode & FMODE_WRITE)
                put_write_access(inode);
+       put_pid(file->f_owner.pid);
        file_kill(file);
        file->f_dentry = NULL;
        file->f_vfsmnt = NULL;
index 21dfadf..e0b6a80 100644 (file)
@@ -1514,7 +1514,7 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
                goto out_unlock;
        }
 
-       error = f_setown(filp, current->pid, 0);
+       error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
 out_unlock:
        unlock_kernel();
        return error;
index 2e29a2e..91c0b2a 100644 (file)
@@ -684,7 +684,8 @@ extern struct block_device *I_BDEV(struct inode *inode);
 
 struct fown_struct {
        rwlock_t lock;          /* protects pid, uid, euid fields */
-       int pid;                /* pid or -pgrp where SIGIO should be sent */
+       struct pid *pid;        /* pid or -pgrp where SIGIO should be sent */
+       enum pid_type pid_type; /* Kind of process group SIGIO should be sent to */
        uid_t uid, euid;        /* uid/euid of process setting the owner */
        int signum;             /* posix.1b rt signal to be delivered on IO */
 };
@@ -880,8 +881,10 @@ extern void kill_fasync(struct fasync_struct **, int, int);
 /* only for net: no internal synchronization */
 extern void __kill_fasync(struct fasync_struct *, int, int);
 
+extern int __f_setown(struct file *filp, struct pid *, enum pid_type, int force);
 extern int f_setown(struct file *filp, unsigned long arg, int force);
 extern void f_delown(struct file *filp);
+extern pid_t f_getown(struct file *filp);
 extern int send_sigurg(struct fown_struct *fown);
 
 /*
index 4b6770e..4aaf919 100644 (file)
@@ -1527,7 +1527,7 @@ static int futex_fd(u32 __user *uaddr, int signal)
        filp->f_mapping = filp->f_dentry->d_inode->i_mapping;
 
        if (signal) {
-               err = f_setown(filp, current->pid, 1);
+               err = __f_setown(filp, task_pid(current), PIDTYPE_PID, 1);
                if (err < 0) {
                        goto error;
                }
index 01918f7..6c9b9b3 100644 (file)
@@ -825,7 +825,7 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
                        break;
                case FIOGETOWN:
                case SIOCGPGRP:
-                       err = put_user(sock->file->f_owner.pid,
+                       err = put_user(f_getown(sock->file),
                                       (int __user *)argp);
                        break;
                case SIOCGIFBR: