[hurd] 07/75: random: satisfy arbitrarily-sized reads

[Samuel Thibault]

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sthibault pushed a commit to branch dde
in repository hurd.

commit df778cd01505e3a8c11f5b13f5ee26a4be290f9a
Author: Justus Winter <address@hidden>
Date:   Fri Nov 6 14:42:04 2015 +0100

    random: satisfy arbitrarily-sized reads
    
    * random/random.c (trivfs_S_io_read): Satisfy arbitrarily-sized reads.
---
 random/random.c | 41 ++++++++++++++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 11 deletions(-)

diff --git a/random/random.c b/random/random.c
index f926b7f..8f76c5b 100644
--- a/random/random.c
+++ b/random/random.c
@@ -143,6 +143,11 @@ trivfs_S_io_read (struct trivfs_protid *cred,
                  data_t *data, mach_msg_type_number_t *data_len,
                  loff_t offs, mach_msg_type_number_t amount)
 {
+  error_t err;
+  mach_msg_type_number_t read_amount = 0;
+  void *buf = NULL;
+  size_t length;
+
   /* Deny access if they have bad credentials. */
   if (! cred)
     return EOPNOTSUPP;
@@ -151,21 +156,27 @@ trivfs_S_io_read (struct trivfs_protid *cred,
 
   pthread_mutex_lock (&global_lock);
 
-  if (amount > 0)
+  while (amount > 0)
     {
       mach_msg_type_number_t new_amount;
+      /* XXX: It would be nice to fix readable_pool to work for sizes
+        greater than the POOLSIZE.  Otherwise we risk detecting too
+        late that we run out of entropy and all that entropy is
+        wasted.  */
       while (readable_pool (amount, level) == 0)
        {
          if (cred->po->openmodes & O_NONBLOCK)
            {
              pthread_mutex_unlock (&global_lock);
-             return EWOULDBLOCK;
+             err = EWOULDBLOCK;
+             goto errout;
            }
          read_blocked = 1;
          if (pthread_hurd_cond_wait_np (&wait, &global_lock))
            {
              pthread_mutex_unlock (&global_lock);
-             return EINTR;
+             err = EINTR;
+             goto errout;
            }
          /* See term/users.c for possible race?  */
        }
@@ -175,27 +186,35 @@ trivfs_S_io_read (struct trivfs_protid *cred,
        {
          *data = mmap (0, amount, PROT_READ|PROT_WRITE,
                                       MAP_ANON, 0, 0);
+
          if (*data == MAP_FAILED)
            {
              pthread_mutex_unlock (&global_lock);
              return errno;
            }
-       }
 
-      new_amount = read_pool ((byte *) *data, amount, level);
+         /* Keep track of our map in case of errors.  */
+         buf = *data, length = amount;
 
-      if (new_amount < amount)
-       munmap (*data + round_page (new_amount),
-               round_page(amount) - round_page (new_amount));
-      amount = new_amount;
+         /* Update DATA_LEN to reflect the new buffers size.  */
+         *data_len = amount;
+       }
+
+      new_amount = read_pool (((byte *) *data) + read_amount, amount, level);
+      read_amount += new_amount;
+      amount -= new_amount;
     }
-  *data_len = amount;
 
   /* Set atime, see term/users.c */
 
   pthread_mutex_unlock (&global_lock);
-
+  *data_len = read_amount;
   return 0;
+
+ errout:
+  if (buf)
+    munmap (buf, length);
+  return err;
 }
 
 /* Write data to an IO object.  If offset is -1, write at the object

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