[PATCH 0/3] get_signal: minor cleanups and fix

[PATCH 0/3] get_signal: minor cleanups and fix

[Oleg Nesterov]

Wen, as you can see I have changed my mind again ;)

Lets remove this clear_siginfo() right now. It is incomplete (and thus
looks confusing) and unnecessary.

See also 2/3, PF_USER_WORKER's already don't get a fully initialized ksig
anyway.

Do you see anything wrong?

Oleg.

[PATCH 1/3] get_signal: don't abuse ksig->info.si_signo and ksig->sig

[Oleg Nesterov]

Cleanup and preparation for the next changes.

get_signal() uses signr or ksig->info.si_signo or ksig->sig in a chaotic
way, this looks confusing. Change it to always use signr.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/signal.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index c9c57d053ce4..09a6dd07cf6b 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2842,7 +2842,7 @@ bool get_signal(struct ksignal *ksig)
 				spin_lock_irq(&sighand->siglock);
 			}
 
-			if (likely(do_signal_stop(ksig->info.si_signo))) {
+			if (likely(do_signal_stop(signr))) {
 				/* It released the siglock.  */
 				goto relock;
 			}
@@ -2866,7 +2866,7 @@ bool get_signal(struct ksignal *ksig)
 
 		if (sig_kernel_coredump(signr)) {
 			if (print_fatal_signals)
-				print_fatal_signal(ksig->info.si_signo);
+				print_fatal_signal(signr);
 			proc_coredump_connector(current);
 			/*
 			 * If it was able to dump core, this kills all
@@ -2890,7 +2890,7 @@ bool get_signal(struct ksignal *ksig)
 		/*
 		 * Death signals, no core dump.
 		 */
-		do_group_exit(ksig->info.si_signo);
+		do_group_exit(signr);
 		/* NOTREACHED */
 	}
 	spin_unlock_irq(&sighand->siglock);
@@ -2900,7 +2900,7 @@ bool get_signal(struct ksignal *ksig)
 	if (!(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
 		hide_si_addr_tag_bits(ksig);
 
-	return ksig->sig > 0;
+	return signr > 0;
 }
 
 /**
-- 
2.25.1.362.g51ebf55

[PATCH 2/3] get_signal: hide_si_addr_tag_bits: fix the usage of uninitialized ksig

[Oleg Nesterov]

ksig->ka and ksig->info are not initialized if get_signal() returns 0 or
if the caller is PF_USER_WORKER.

Check signr != 0 before SA_EXPOSE_TAGBITS and move the "out" label down.

The latter means that ksig->sig won't be initialized if a PF_USER_WORKER
thread gets a fatal signal but this is fine, PF_USER_WORKER's don't use
ksig. And there is nothing new, in this case ksig->ka and ksig-info are
not initialized anyway. Add a comment.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/signal.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 09a6dd07cf6b..a69d3069067a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2881,8 +2881,9 @@ bool get_signal(struct ksignal *ksig)
 
 		/*
 		 * PF_USER_WORKER threads will catch and exit on fatal signals
-		 * themselves. They have cleanup that must be performed, so
-		 * we cannot call do_exit() on their behalf.
+		 * themselves. They have cleanup that must be performed, so we
+		 * cannot call do_exit() on their behalf. Note that ksig won't
+		 * be properly initialized, PF_USER_WORKER's shouldn't use it.
 		 */
 		if (current->flags & PF_USER_WORKER)
 			goto out;
@@ -2894,12 +2895,12 @@ bool get_signal(struct ksignal *ksig)
 		/* NOTREACHED */
 	}
 	spin_unlock_irq(&sighand->siglock);
-out:
+
 	ksig->sig = signr;
 
-	if (!(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
+	if (signr && !(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
 		hide_si_addr_tag_bits(ksig);
-
+out:
 	return signr > 0;
 }
 
-- 
2.25.1.362.g51ebf55

[PATCH 3/3] get_signal: don't initialize ksig->info if SIGNAL_GROUP_EXIT/group_exec_task

[Oleg Nesterov]

This initialization is incomplete and unnecessary, neither do_group_exit()
nor PF_USER_WORKER need ksig->info.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/signal.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index a69d3069067a..9c6a5ccac328 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2727,12 +2727,15 @@ bool get_signal(struct ksignal *ksig)
 		/* Has this task already been marked for death? */
 		if ((signal->flags & SIGNAL_GROUP_EXIT) ||
 		     signal->group_exec_task) {
-			clear_siginfo(&ksig->info);
-			ksig->info.si_signo = signr = SIGKILL;
+			signr = SIGKILL;
 			sigdelset(&current->pending.signal, SIGKILL);
 			trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
-				&sighand->action[SIGKILL - 1]);
+					     &sighand->action[SIGKILL-1]);
 			recalc_sigpending();
+			/*
+			 * implies do_group_exit() or return to PF_USER_WORKER,
+			 * no need to initialize ksig->info/etc.
+			 */
 			goto fatal;
 		}
 
-- 
2.25.1.362.g51ebf55