bin/sh: Fix history long line truncation/corruption

When reading from standard input with editline history enabled, increase
buffer size to accomodate long lines so that history is recorded
correctly. Cleanup el_gets() handling avoiding potentially dangerous
retention of pointers to editline buffers across calls.  Ensure struct
parsefile objects are properly zero initialised when created. Remove
push argument from setinputstring() and simplify logic as it was always
called with a value of one and as was written was potentially dangerous
if ever called with a value of zero.

This commit does not fix long lines when history is enabled but editing
is not (e.g. if there is no terminal).

MFC after:	3 weeks
Pull Request:	https://github.com/freebsd/freebsd-src/pull/2028
Signed-off-by: Kristofer Peterson <kris@tranception.com>

4 files changed, 76 insertions, 78 deletions

diff --git a/bin/sh/eval.c b/bin/sh/eval.c
index 0c41c5e69eea..b4c1924f04ad 100644
--- a/bin/sh/eval.c
+++ b/bin/sh/eval.c
@@ -154,7 +154,7 @@ evalstring(const char *s, int flags)
 	flags &= ~EV_EXIT;
 	any = 0;
 	setstackmark(&smark);
-	setinputstring(s, 1);
+	setinputstring(s);
 	while ((n = parsecmd(0)) != NEOF) {
 		if (n != NULL && !nflag) {
 			if (flags_exit && preadateof())
diff --git a/bin/sh/input.c b/bin/sh/input.c
index e88d31be12be..c916fb29178b 100644
--- a/bin/sh/input.c
+++ b/bin/sh/input.c
@@ -81,6 +81,7 @@ struct parsefile {
 	int lleft;		/* number of lines left in this buffer */
 	const char *nextc;	/* next char in buffer */
 	char *buf;		/* input buffer */
+	size_t bufsize;		/* input buffer size */
 	struct strpush *strpush; /* for pushing strings at this level */
 	struct strpush basestrpush; /* so pushing one is fast */
 };
@@ -93,7 +94,8 @@ const char *parsenextc;		/* copy of parsefile->nextc */
 static char basebuf[BUFSIZ + 1];/* buffer for top level input file */
 static struct parsefile basepf = {	/* top level input file */
 	.nextc = basebuf,
-	.buf = basebuf
+	.buf = basebuf,
+	.bufsize = sizeof(basebuf),
 };
 static struct parsefile *parsefile = &basepf;	/* current input file */
 int whichprompt;		/* 1 == PS1, 2 == PS2 */
@@ -127,52 +129,61 @@ static int
 preadfd(void)
 {
 	int nr;
-	parsenextc = parsefile->buf;
 
 retry:
 #ifndef NO_HISTORY
 	if (parsefile->fd == 0 && el) {
-		static const char *rl_cp;
-		static int el_len;
-
-		if (rl_cp == NULL) {
-			el_resize(el);
-			rl_cp = el_gets(el, &el_len);
-		}
-		if (rl_cp == NULL)
-			nr = el_len == 0 ? 0 : -1;
-		else {
-			nr = el_len;
-			if (nr > BUFSIZ)
-				nr = BUFSIZ;
-			memcpy(parsefile->buf, rl_cp, nr);
-			if (nr != el_len) {
-				el_len -= nr;
-				rl_cp += nr;
-			} else
-				rl_cp = NULL;
+		const char *line;
+
+		el_resize(el);
+		line = el_gets(el, &nr);
+		if (nr > 0 && parsefile->bufsize < (size_t)nr + 1) {
+			size_t bufsize;
+
+			INTOFF;
+			if (parsefile->buf != basebuf) {
+				ckfree(parsefile->buf);
+				parsefile->buf = NULL;
+				parsefile->bufsize = 0;
+			}
+			bufsize = (size_t)nr + BUFSIZ + 1;
+			bufsize -= bufsize % BUFSIZ;
+			parsefile->buf = ckmalloc(bufsize);
+			parsefile->bufsize = bufsize;
+			INTON;
 		}
+		if (nr > 0 && line != NULL)
+			memcpy(parsefile->buf, line, nr);
+		else
+			nr = nr ? -1 : 0;
 	} else
 #endif
-		nr = read(parsefile->fd, parsefile->buf, BUFSIZ);
-
-	if (nr <= 0) {
-                if (nr < 0) {
-                        if (errno == EINTR)
-                                goto retry;
-                        if (parsefile->fd == 0 && errno == EWOULDBLOCK) {
-                                int flags = fcntl(0, F_GETFL, 0);
-                                if (flags >= 0 && flags & O_NONBLOCK) {
-                                        flags &=~ O_NONBLOCK;
-                                        if (fcntl(0, F_SETFL, flags) >= 0) {
-						out2fmt_flush("sh: turning off NDELAY mode\n");
-                                                goto retry;
-                                        }
-                                }
-                        }
+	nr = read(parsefile->fd, parsefile->buf, parsefile->bufsize - 1);
+
+	if (nr < 0)
+		switch (errno) {
+			int flags;
+
+		case EINTR:
+			goto retry;
+		case EWOULDBLOCK:
+			if (parsefile->fd != 0)
+				break;
+			if ((flags = fcntl(0, F_GETFL, 0)) < 0)
+				break;
+			if (!(flags & O_NONBLOCK))
+				break;
+			if (fcntl(0, F_SETFL, flags & ~O_NONBLOCK) < 0)
+				break;
+			out2fmt_flush("sh: turning off NDELAY mode\n");
+			goto retry;
                 }
-                nr = -1;
-	}
+	else if (nr > 0)
+		parsefile->buf[nr] = '\0';
+	else
+		nr = -1;
+
+	parsenextc = parsefile->buf;
 	return nr;
 }
 
@@ -189,7 +200,8 @@ retry:
 int
 preadbuffer(void)
 {
-	char *p, *q, *r, *end;
+	const char *end;
+	char *q, *r;
 	char savec;
 
 	while (parsefile->strpush) {
@@ -208,31 +220,22 @@ preadbuffer(void)
 		return PEOF;
 
 again:
-	if (parselleft <= 0) {
-		if ((parselleft = preadfd()) == -1) {
-			parselleft = parsenleft = EOF_NLEFT;
-			return PEOF;
-		}
+	if (parselleft <= 0 && (parselleft = preadfd()) == -1) {
+		parselleft = parsenleft = EOF_NLEFT;
+		return (PEOF);
 	}
-
-	p = parsefile->buf + (parsenextc - parsefile->buf);
-	end = p + parselleft;
-	*end = '\0';
-	q = strchrnul(p, '\n');
-	if (q != end && *q == '\0') {
+	end = parsenextc + parselleft;
+	q = strchrnul(parsenextc, '\n');
+	if (*q == '\0' && q != end) {
 		/* delete nul characters */
-		for (r = q; q != end; q++) {
+		for (r = q++; q != end; q++)
 			if (*q != '\0')
 				*r++ = *q;
-		}
-		parselleft -= end - r;
-		if (parselleft == 0)
-			goto again;
-		end = p + parselleft;
-		*end = '\0';
-		q = strchrnul(p, '\n');
+		*r = '\0';
+		parselleft = r - parsenextc;
+		goto again;
 	}
-	if (q == end) {
+	if (*q == '\0') {
 		parsenleft = parselleft;
 		parselleft = 0;
 	} else /* *q == '\n' */ {
@@ -307,7 +310,7 @@ pushstring(const char *s, int len, struct alias *ap)
 	INTOFF;
 /*out2fmt_flush("*** calling pushstring: %s, %d\n", s, len);*/
 	if (parsefile->strpush) {
-		sp = ckmalloc(sizeof (struct strpush));
+		sp = ckmalloc(sizeof(struct strpush));
 		sp->prev = parsefile->strpush;
 		parsefile->strpush = sp;
 	} else
@@ -391,15 +394,15 @@ setinputfile(const char *fname, int push, int verify)
 void
 setinputfd(int fd, int push)
 {
-	if (push) {
+	if (push)
 		pushfile();
-		parsefile->buf = ckmalloc(BUFSIZ + 1);
-	}
 	if (parsefile->fd > 0)
 		close(parsefile->fd);
 	parsefile->fd = fd;
-	if (parsefile->buf == NULL)
+	if (parsefile->buf == NULL) {
 		parsefile->buf = ckmalloc(BUFSIZ + 1);
+		parsefile->bufsize = BUFSIZ + 1;
+	}
 	parselleft = parsenleft = 0;
 	plinno = 1;
 }
@@ -410,14 +413,12 @@ setinputfd(int fd, int push)
  */
 
 void
-setinputstring(const char *string, int push)
+setinputstring(const char *string)
 {
 	INTOFF;
-	if (push)
-		pushfile();
+	pushfile();
 	parsenextc = string;
 	parselleft = parsenleft = strlen(string);
-	parsefile->buf = NULL;
 	plinno = 1;
 	INTON;
 }
@@ -434,15 +435,12 @@ pushfile(void)
 {
 	struct parsefile *pf;
 
+	pf = (struct parsefile *)ckmalloc(sizeof(struct parsefile));
+	*pf = (struct parsefile){ .prev = parsefile, .fd = -1 };
 	parsefile->nleft = parsenleft;
 	parsefile->lleft = parselleft;
 	parsefile->nextc = parsenextc;
 	parsefile->linno = plinno;
-	pf = (struct parsefile *)ckmalloc(sizeof (struct parsefile));
-	pf->prev = parsefile;
-	pf->fd = -1;
-	pf->strpush = NULL;
-	pf->basestrpush.prev = NULL;
 	parsefile = pf;
 }
 
diff --git a/bin/sh/input.h b/bin/sh/input.h
index 70e6b06c72da..4e8992a5bf60 100644
--- a/bin/sh/input.h
+++ b/bin/sh/input.h
@@ -54,7 +54,7 @@ void pungetc(void);
 void pushstring(const char *, int, struct alias *);
 void setinputfile(const char *, int, int);
 void setinputfd(int, int);
-void setinputstring(const char *, int);
+void setinputstring(const char *);
 void popfile(void);
 struct parsefile *getcurrentfile(void);
 void popfilesupto(struct parsefile *);
diff --git a/bin/sh/parser.c b/bin/sh/parser.c
index 3e42d41caec4..f6ef8d807704 100644
--- a/bin/sh/parser.c
+++ b/bin/sh/parser.c
@@ -1167,7 +1167,7 @@ parsebackq(char *out, struct nodelist **pbqlist,
 		INTOFF;
 		ostr = ckmalloc(olen);
 		memcpy(ostr, stackblock(), olen);
-		setinputstring(ostr, 1);
+		setinputstring(ostr);
 		INTON;
         }
 	nlpp = pbqlist;
@@ -2368,7 +2368,7 @@ expandstr(const char *ps)
 	if (!setjmp(jmploc.loc)) {
 		handler = &jmploc;
 		parser_temp = NULL;
-		setinputstring(ps, 1);
+		setinputstring(ps);
 		doprompt = 0;
 		readtoken1(pgetc(), DQSYNTAX, NOEOFMARK, 0);
 		if (backquotelist != NULL)