[Bug-wget] [PATCH] Fix signal race condition

[Tobias Stoeckmann]

The signal handler for SIGALRM calls longjmp, but the handler is
installed before the jump target has been initialized. If another
process sends SIGALRM right between handler installation and target
initialization, the jump leads to undefined behavior.

This can easily be fixed by moving the signal handler installation
into the "SETJMP == 0" conditional block, which means that the target
has just been initialized.

Signed-off-by: Tobias Stoeckmann <address@hidden>
---
 src/utils.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/utils.c b/src/utils.c
index b07da9f..e42bb8f 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -2045,13 +2045,16 @@ run_with_timeout (double timeout, void (*fun) (void *), 
void *arg)
       return false;
     }
 
-  signal (SIGALRM, abort_run_with_timeout);
   if (SETJMP (run_with_timeout_env) != 0)
     {
       /* Longjumped out of FUN with a timeout. */
       signal (SIGALRM, SIG_DFL);
       return true;
     }
+  else
+    {
+      signal (SIGALRM, abort_run_with_timeout);
+    }
   alarm_set (timeout);
   fun (arg);
 
-- 
2.9.2