From 7a962424149cc60f3a187d0213a12689dd5e806b Mon Sep 17 00:00:00 2001
From: Tony Cook <tony@develop-help.com>
Date: Mon, 14 Aug 2017 11:52:39 +1000
Subject: [PATCH] (perl #131746) avoid undefined behaviour in Copy() etc
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These functions depend on C library functions which have undefined
behaviour when passed NULL pointers, even when passed a zero 'n' value.

Some compilers use this information, ie. assume the pointers are
non-NULL when optimizing any following code, so we do need to
prevent such unguarded calls.

My initial thought was to add conditionals to each macro to skip the
call to the library function when n is zero, but this adds a cost to
every use of these macros, even when the n value is always true.

So instead I added asserts() which will give us a much more visible
indicator of such broken code and revealed the pp_caller and Glob.xs
issues also patched here.

Petr Písař: Ported to 5.26.1 from
f14cf3632059d421de83cf901c7e849adc1fcd03.

Signed-off-by: Petr Písař <ppisar@redhat.com>
---
 ext/File-Glob/Glob.xs |  2 +-
 handy.h               | 14 +++++++-------
 pp_ctl.c              |  3 ++-
 pp_hot.c              |  3 ++-
 4 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/ext/File-Glob/Glob.xs b/ext/File-Glob/Glob.xs
index e0a3681..9779d54 100644
--- a/ext/File-Glob/Glob.xs
+++ b/ext/File-Glob/Glob.xs
@@ -121,7 +121,7 @@ iterate(pTHX_ bool(*globber)(pTHX_ AV *entries, const char *pat, STRLEN len, boo
 
     /* chuck it all out, quick or slow */
     if (gimme == G_ARRAY) {
-	if (!on_stack) {
+	if (!on_stack && AvFILLp(entries) + 1) {
 	    EXTEND(SP, AvFILLp(entries)+1);
 	    Copy(AvARRAY(entries), SP+1, AvFILLp(entries)+1, SV *);
 	    SP += AvFILLp(entries)+1;
diff --git a/handy.h b/handy.h
index 80f9cf4..88b5b55 100644
--- a/handy.h
+++ b/handy.h
@@ -2409,17 +2409,17 @@ void Perl_mem_log_del_sv(const SV *sv, const char *filename, const int linenumbe
 #define Safefree(d)	safefree(MEM_LOG_FREE((Malloc_t)(d)))
 #endif
 
-#define Move(s,d,n,t)	(MEM_WRAP_CHECK_(n,t) (void)memmove((char*)(d),(const char*)(s), (n) * sizeof(t)))
-#define Copy(s,d,n,t)	(MEM_WRAP_CHECK_(n,t) (void)memcpy((char*)(d),(const char*)(s), (n) * sizeof(t)))
-#define Zero(d,n,t)	(MEM_WRAP_CHECK_(n,t) (void)memzero((char*)(d), (n) * sizeof(t)))
+#define Move(s,d,n,t)	(MEM_WRAP_CHECK_(n,t) assert(d), assert(s), (void)memmove((char*)(d),(const char*)(s), (n) * sizeof(t)))
+#define Copy(s,d,n,t)	(MEM_WRAP_CHECK_(n,t) assert(d), assert(s), (void)memcpy((char*)(d),(const char*)(s), (n) * sizeof(t)))
+#define Zero(d,n,t)	(MEM_WRAP_CHECK_(n,t) assert(d), (void)memzero((char*)(d), (n) * sizeof(t)))
 
-#define MoveD(s,d,n,t)	(MEM_WRAP_CHECK_(n,t) memmove((char*)(d),(const char*)(s), (n) * sizeof(t)))
-#define CopyD(s,d,n,t)	(MEM_WRAP_CHECK_(n,t) memcpy((char*)(d),(const char*)(s), (n) * sizeof(t)))
+#define MoveD(s,d,n,t)	(MEM_WRAP_CHECK_(n,t) assert(d), assert(s), memmove((char*)(d),(const char*)(s), (n) * sizeof(t)))
+#define CopyD(s,d,n,t)	(MEM_WRAP_CHECK_(n,t) assert(d), assert(s), memcpy((char*)(d),(const char*)(s), (n) * sizeof(t)))
 #ifdef HAS_MEMSET
-#define ZeroD(d,n,t)	(MEM_WRAP_CHECK_(n,t) memzero((char*)(d), (n) * sizeof(t)))
+#define ZeroD(d,n,t)	(MEM_WRAP_CHECK_(n,t) assert(d), memzero((char*)(d), (n) * sizeof(t)))
 #else
 /* Using bzero(), which returns void.  */
-#define ZeroD(d,n,t)	(MEM_WRAP_CHECK_(n,t) memzero((char*)(d), (n) * sizeof(t)),d)
+#define ZeroD(d,n,t)	(MEM_WRAP_CHECK_(n,t) assert(d), memzero((char*)(d), (n) * sizeof(t)),d)
 #endif
 
 #define PoisonWith(d,n,t,b)	(MEM_WRAP_CHECK_(n,t) (void)memset((char*)(d), (U8)(b), (n) * sizeof(t)))
diff --git a/pp_ctl.c b/pp_ctl.c
index 15c193b..f1c57bc 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -1971,7 +1971,8 @@ PP(pp_caller)
 
 	if (AvMAX(PL_dbargs) < AvFILLp(ary) + off)
 	    av_extend(PL_dbargs, AvFILLp(ary) + off);
-	Copy(AvALLOC(ary), AvARRAY(PL_dbargs), AvFILLp(ary) + 1 + off, SV*);
+        if (AvFILLp(ary) + 1 + off)
+            Copy(AvALLOC(ary), AvARRAY(PL_dbargs), AvFILLp(ary) + 1 + off, SV*);
 	AvFILLp(PL_dbargs) = AvFILLp(ary) + off;
     }
     mPUSHi(CopHINTS_get(cx->blk_oldcop));
diff --git a/pp_hot.c b/pp_hot.c
index 5899413..66b79ea 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -4138,7 +4138,8 @@ PP(pp_entersub)
                 AvARRAY(av) = ary;
             }
 
-	    Copy(MARK+1,AvARRAY(av),items,SV*);
+            if (items)
+                Copy(MARK+1,AvARRAY(av),items,SV*);
 	    AvFILLp(av) = items - 1;
 	}
 	if (UNLIKELY((cx->blk_u16 & OPpENTERSUB_LVAL_MASK) == OPpLVAL_INTRO &&
-- 
2.13.6