fs/locks: don't mess with the address limit in compat_fcntl64

Instead write a proper compat syscall that calls common helpers.

[ jlayton: fix pointer dereferencing in fixup_compat_flock ]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>

diff --git a/fs/fcntl.c b/fs/fcntl.c
index ed4283d..bbf8034 100644 (file)
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -506,76 +506,92 @@ convert_fcntl_cmd(unsigned int cmd)
        return cmd;
 }
 
+/*
+ * GETLK was successful and we need to return the data, but it needs to fit in
+ * the compat structure.
+ * l_start shouldn't be too big, unless the original start + end is greater than
+ * COMPAT_OFF_T_MAX, in which case the app was asking for trouble, so we return
+ * -EOVERFLOW in that case.  l_len could be too big, in which case we just
+ * truncate it, and only allow the app to see that part of the conflicting lock
+ * that might make sense to it anyway
+ */
+static int fixup_compat_flock(struct flock *flock)
+{
+       if (flock->l_start > COMPAT_OFF_T_MAX)
+               return -EOVERFLOW;
+       if (flock->l_len > COMPAT_OFF_T_MAX)
+               flock->l_len = COMPAT_OFF_T_MAX;
+       return 0;
+}
+
 COMPAT_SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
                       compat_ulong_t, arg)
 {
-       mm_segment_t old_fs;
-       struct flock f;
-       long ret;
-       unsigned int conv_cmd;
+       struct fd f = fdget_raw(fd);
+       struct flock flock;
+       long err = -EBADF;
+
+       if (!f.file)
+               return err;
+
+       if (unlikely(f.file->f_mode & FMODE_PATH)) {
+               if (!check_fcntl_cmd(cmd))
+                       goto out_put;
+       }
+
+       err = security_file_fcntl(f.file, cmd, arg);
+       if (err)
+               goto out_put;
 
        switch (cmd) {
        case F_GETLK:
+               err = get_compat_flock(&flock, compat_ptr(arg));
+               if (err)
+                       break;
+               err = fcntl_getlk(f.file, convert_fcntl_cmd(cmd), &flock);
+               if (err)
+                       break;
+               err = fixup_compat_flock(&flock);
+               if (err)
+                       return err;
+               err = put_compat_flock(&flock, compat_ptr(arg));
+               break;
+       case F_GETLK64:
+       case F_OFD_GETLK:
+               err = get_compat_flock64(&flock, compat_ptr(arg));
+               if (err)
+                       break;
+               err = fcntl_getlk(f.file, convert_fcntl_cmd(cmd), &flock);
+               if (err)
+                       break;
+               err = fixup_compat_flock(&flock);
+               if (err)
+                       return err;
+               err = put_compat_flock64(&flock, compat_ptr(arg));
+               break;
        case F_SETLK:
        case F_SETLKW:
-               ret = get_compat_flock(&f, compat_ptr(arg));
-               if (ret != 0)
+               err = get_compat_flock(&flock, compat_ptr(arg));
+               if (err)
                        break;
-               old_fs = get_fs();
-               set_fs(KERNEL_DS);
-               ret = sys_fcntl(fd, cmd, (unsigned long)&f);
-               set_fs(old_fs);
-               if (cmd == F_GETLK && ret == 0) {
-                       /* GETLK was successful and we need to return the data...
-                        * but it needs to fit in the compat structure.
-                        * l_start shouldn't be too big, unless the original
-                        * start + end is greater than COMPAT_OFF_T_MAX, in which
-                        * case the app was asking for trouble, so we return
-                        * -EOVERFLOW in that case.
-                        * l_len could be too big, in which case we just truncate it,
-                        * and only allow the app to see that part of the conflicting
-                        * lock that might make sense to it anyway
-                        */
-
-                       if (f.l_start > COMPAT_OFF_T_MAX)
-                               ret = -EOVERFLOW;
-                       if (f.l_len > COMPAT_OFF_T_MAX)
-                               f.l_len = COMPAT_OFF_T_MAX;
-                       if (ret == 0)
-                               ret = put_compat_flock(&f, compat_ptr(arg));
-               }
+               err = fcntl_setlk(fd, f.file, convert_fcntl_cmd(cmd), &flock);
                break;
-
-       case F_GETLK64:
        case F_SETLK64:
        case F_SETLKW64:
-       case F_OFD_GETLK:
        case F_OFD_SETLK:
        case F_OFD_SETLKW:
-               ret = get_compat_flock64(&f, compat_ptr(arg));
-               if (ret != 0)
+               err = get_compat_flock64(&flock, compat_ptr(arg));
+               if (err)
                        break;
-               old_fs = get_fs();
-               set_fs(KERNEL_DS);
-               conv_cmd = convert_fcntl_cmd(cmd);
-               ret = sys_fcntl(fd, conv_cmd, (unsigned long)&f);
-               set_fs(old_fs);
-               if ((conv_cmd == F_GETLK || conv_cmd == F_OFD_GETLK) && ret == 0) {
-                       /* need to return lock information - see above for commentary */
-                       if (f.l_start > COMPAT_LOFF_T_MAX)
-                               ret = -EOVERFLOW;
-                       if (f.l_len > COMPAT_LOFF_T_MAX)
-                               f.l_len = COMPAT_LOFF_T_MAX;
-                       if (ret == 0)
-                               ret = put_compat_flock64(&f, compat_ptr(arg));
-               }
+               err = fcntl_setlk(fd, f.file, convert_fcntl_cmd(cmd), &flock);
                break;
-
        default:
-               ret = sys_fcntl(fd, cmd, arg);
+               err = do_fcntl(fd, cmd, arg, f.file);
                break;
        }
-       return ret;
+out_put:
+       fdput(f);
+       return err;
 }
 
 COMPAT_SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd,