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authorSamuel Thibault <samuel.thibault@ens-lyon.org>2018-10-09 23:40:09 +0200
committerSamuel Thibault <samuel.thibault@ens-lyon.org>2018-10-28 13:41:51 +0100
commit5c81be53407434ce22b849722a3d691295480016 (patch)
tree930f36f9263b5d02c176d6b13b0ed5a762c8fd83 /hurd
parent2d0d1d38761cd9aeb7063c5cce1993cec909f67f (diff)
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hurd: Fix race between calling RPC and handling a signal
	* sysdeps/mach/hurd/i386/intr-msg.h (INTR_MSG_TRAP): Make
	_hurd_intr_rpc_msg_about_to global point to start of controlled
	assembly snippet. Make it check canceled flag.
	* hurd/hurdsig.c (_hurdsig_abort_rpcs): Only mutate thread if it passed
	the _hurd_intr_rpc_msg_about_to point.
	* hurd/intr-msg.c (_hurd_intr_rpc_mach_msg): Remove comment on mutation
	issue, remove cancel flag check.
Diffstat (limited to 'hurd')
-rw-r--r--hurd/hurdsig.c4
-rw-r--r--hurd/intr-msg.c17
2 files changed, 5 insertions, 16 deletions
diff --git a/hurd/hurdsig.c b/hurd/hurdsig.c
index 48179b4197..d105615e42 100644
--- a/hurd/hurdsig.c
+++ b/hurd/hurdsig.c
@@ -292,6 +292,7 @@ _hurdsig_abort_rpcs (struct hurd_sigstate *ss, int signo, int sigthread,
 		     struct machine_thread_all_state *state, int *state_change,
 		     void (*reply) (void))
 {
+  extern const void _hurd_intr_rpc_msg_about_to;
   extern const void _hurd_intr_rpc_msg_in_trap;
   mach_port_t rcv_port = MACH_PORT_NULL;
   mach_port_t intr_port;
@@ -307,7 +308,8 @@ _hurdsig_abort_rpcs (struct hurd_sigstate *ss, int signo, int sigthread,
      receive completes immediately or aborts.  */
   abort_thread (ss, state, reply);
 
-  if (state->basic.PC < (natural_t) &_hurd_intr_rpc_msg_in_trap)
+  if (state->basic.PC >= (natural_t) &_hurd_intr_rpc_msg_about_to &&
+      state->basic.PC <  (natural_t) &_hurd_intr_rpc_msg_in_trap)
     {
       /* The thread is about to do the RPC, but hasn't yet entered
 	 mach_msg.  Mutate the thread's state so it knows not to try
diff --git a/hurd/intr-msg.c b/hurd/intr-msg.c
index 1f7724ee8b..7ace0a16b3 100644
--- a/hurd/intr-msg.c
+++ b/hurd/intr-msg.c
@@ -114,23 +114,10 @@ _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
 
  message:
 
-  /* XXX
-     At all points here (once SS->intr_port is set), the signal thread
-     thinks we are "about to enter the syscall", and might mutate our
-     return-value register.  This is bogus.
-   */
-
-  if (ss->cancel)
-    {
-      /* We have been cancelled.  Don't do an RPC at all.  */
-      ss->intr_port = MACH_PORT_NULL;
-      ss->cancel = 0;
-      return EINTR;
-    }
-
   /* Note that the signal trampoline code might modify our OPTION!  */
   err = INTR_MSG_TRAP (msg, option, send_size,
-		       rcv_size, rcv_name, timeout, notify);
+		       rcv_size, rcv_name, timeout, notify,
+		       &ss->cancel, &ss->intr_port);
 
   switch (err)
     {