ksh segfaults in job_chksave after receiving SIGCHLD

Upstreaming Debian patch: Prior to this update, the compiler optimization dropped parts from the ksh job locking mechanism from the binary code. As a consequence, ksh could terminate unexpectedly with a segmentation fault after it received the SIGCHLD signal. This update implements a fix to ensure the compiler does not drop parts of the ksh mechanism and the crash no longer occurs. Author: Michal Hlavinka [email protected] Origin: Red Hat fix, ksh-20120801-locking.patch Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1123467 Bug-Ubuntu: https://bugs.launchpad.net/bugs/1697501 Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=867181
ksh93 · Jun 14, 2020 · 07cc71b · 07cc71b
1 parent 5498d9e
commit 07cc71b
Showing 1 changed file with 7 additions and 4 deletions.
diff --git a/src/cmd/ksh93/include/jobs.h b/src/cmd/ksh93/include/jobs.h
@@ -149,15 +149,18 @@ extern struct jobs job;
 #define vmbusy()	0
 #endif
 
-#define job_lock()	(job.in_critical++)
+#define asoincint(p)  __sync_fetch_and_add(p,1)
+#define asodecint(p)  __sync_fetch_and_sub(p,1)
+
+#define job_lock()	asoincint(&job.in_critical)
 #define job_unlock()	\
 	do { \
 		int	sig; \
-		if (!--job.in_critical && (sig = job.savesig)) \
+		if (asodecint(&job.in_critical)==1 && (sig = job.savesig)) \
 		{ \
-			if (!job.in_critical++ && !vmbusy()) \
+			if (!asoincint(&job.in_critical) && !vmbusy()) \
 				job_reap(sig); \
-			job.in_critical--; \
+			asodecint(&job.in_critical); \
 		} \
 	} while(0)