No cancel signal in unsafe places.

When disabling async cancellation we cannot return from the function
call if the thread is canceled.  This happens when the cancel bits
have been set before async cancel is disabled but the signal hasn't
been sent/received yet.  Delay for as long as necessary since
otherwise the signal might be received in an unsafe context.

1 files changed, 13 insertions, 1 deletions

diff --git a/nptl/libc-cancellation.c b/nptl/libc-cancellation.c
index cf24f1c0f2..35ac82b3d1 100644
--- a/nptl/libc-cancellation.c
+++ b/nptl/libc-cancellation.c
@@ -86,15 +86,17 @@ __libc_disable_asynccancel (int oldtype)
     return;
 
   struct pthread *self = THREAD_SELF;
+  int newval;
 
 #ifdef THREAD_ATOMIC_AND
   THREAD_ATOMIC_AND (self, cancelhandling, ~CANCELTYPE_BITMASK);
+  newval = THREAD_GETMEM (self, cancelhandling);
 #else
   int oldval = THREAD_GETMEM (self, cancelhandling);
 
   while (1)
     {
-      int newval = oldval & ~CANCELTYPE_BITMASK;
+      newval = oldval & ~CANCELTYPE_BITMASK;
 
       if (newval == oldval)
 	break;
@@ -108,6 +110,16 @@ __libc_disable_asynccancel (int oldtype)
       oldval = curval;
     }
 #endif
+
+  /* We cannot return when we are being canceled.  Upon return the
+     thread might be things which would have to be undone.  The
+     following loop should loop until the cancellation signal is
+     delivered.  */
+  while (__builtin_expect (newval & CANCELED_BITMASK, 0))
+    {
+      lll_futex_wait (&self->cancelhandling, newval, LLL_PRIVATE);
+      newval = THREAD_GETMEM (self, cancelhandling);
+    }
 }