bsdgrep: don't allow negative -A / -B / -C

Previously, when given a negative -A/-B/-C argument bsdgrep would
overflow the respective context flag(s) and exhibited surprising
behavior.

Fix this by removing unsignedness of Aflag/Bflag and erroring out if
we're given a value < 0.  Also adjust the type used to track 'tail'
context in procfile() so that it accurately reflects the Aflag value
rather than overflowing and losing trailing context.

This also fixes an inconsistency previously existing between -n and
-C "n" behavior.  They are now both limited to LLONG_MAX, to be
consistent.

Add some test cases to make sure grep errors out properly for both
negative context values as well as non-numeric context values rather
than giving bogus matches.

Submitted by:	Kyle Evans <kevans91@ksu.edu>
Reviewed by:	cem
Differential Revision:	https://reviews.freebsd.org/D10675

contrib/netbsd-tests/usr.bin/grep/t_grep.sh

@@ -517,6 +517,28 @@ grep_nomatch_flags_body()
 	atf_check -o empty grep -q -A 1 -e "B" test1
 	atf_check -o empty grep -q -C 1 -e "B" test1
 }
+
+atf_test_case badcontext
+badcontext_head()
+{
+	atf_set "descr" "Check for handling of invalid context arguments"
+}
+badcontext_body()
+{
+	printf "A\nB\nC\n" > test1
+
+	atf_check -s not-exit:0 -e ignore grep -A "-1" "B" test1
+
+	atf_check -s not-exit:0 -e ignore grep -B "-1" "B" test1
+
+	atf_check -s not-exit:0 -e ignore grep -C "-1" "B" test1
+
+	atf_check -s not-exit:0 -e ignore grep -A "B" "B" test1
+
+	atf_check -s not-exit:0 -e ignore grep -B "B" "B" test1
+
+	atf_check -s not-exit:0 -e ignore grep -C "B" "B" test1
+}
 # End FreeBSD
 
 atf_init_test_cases()
@@ -551,5 +573,6 @@ atf_init_test_cases()
 	atf_add_test_case egrep_sanity
 	atf_add_test_case grep_sanity
 	atf_add_test_case grep_nomatch_flags
+	atf_add_test_case badcontext
 # End FreeBSD
 }

usr.bin/grep/grep.c

@@ -108,8 +108,8 @@ struct epat	*dpattern, *fpattern;
 char	 re_error[RE_ERROR_BUF + 1];
 
 /* Command-line flags */
-unsigned long long Aflag;	/* -A x: print x lines trailing each match */
-unsigned long long Bflag;	/* -B x: print x lines leading each match */
+long long Aflag;	/* -A x: print x lines trailing each match */
+long long Bflag;	/* -B x: print x lines leading each match */
 bool	 Hflag;		/* -H: always print file name */
 bool	 Lflag;		/* -L: only show names of files with no matches */
 bool	 bflag;		/* -b: show block numbers for each match */
@@ -351,7 +351,7 @@ main(int argc, char *argv[])
 	char **aargv, **eargv, *eopts;
 	char *ep;
 	const char *pn;
-	unsigned long long l;
+	long long l;
 	unsigned int aargc, eargc, i;
 	int c, lastc, needpattern, newarg, prevoptind;
 
@@ -438,10 +438,11 @@ main(int argc, char *argv[])
 		case '5': case '6': case '7': case '8': case '9':
 			if (newarg || !isdigit(lastc))
 				Aflag = 0;
-			else if (Aflag > LLONG_MAX / 10) {
+			else if (Aflag > LLONG_MAX / 10 - 1) {
 				errno = ERANGE;
 				err(2, NULL);
 			}
+
 			Aflag = Bflag = (Aflag * 10) + (c - '0');
 			break;
 		case 'C':
@@ -454,14 +455,17 @@ main(int argc, char *argv[])
 			/* FALLTHROUGH */
 		case 'B':
 			errno = 0;
-			l = strtoull(optarg, &ep, 10);
-			if (((errno == ERANGE) && (l == ULLONG_MAX)) ||
-			    ((errno == EINVAL) && (l == 0)))
+			l = strtoll(optarg, &ep, 10);
+			if (errno == ERANGE || errno == EINVAL)
 				err(2, NULL);
 			else if (ep[0] != '\0') {
 				errno = EINVAL;
 				err(2, NULL);
+			} else if (l < 0) {
+				errno = EINVAL;
+				err(2, "context argument must be non-negative");
 			}
+
 			if (c == 'A')
 				Aflag = l;
 			else if (c == 'B')

usr.bin/grep/grep.h

@@ -115,7 +115,7 @@ extern bool	 Eflag, Fflag, Gflag, Hflag, Lflag,
 		 bflag, cflag, hflag, iflag, lflag, mflag, nflag, oflag,
 		 qflag, sflag, vflag, wflag, xflag;
 extern bool	 dexclude, dinclude, fexclude, finclude, lbflag, nullflag;
-extern unsigned long long Aflag, Bflag;
+extern long long Aflag, Bflag;
 extern long long mcount;
 extern long long mlimit;
 extern char	 fileeol;

usr.bin/grep/queue.c

@@ -49,7 +49,7 @@ struct qentry {
 };
 
 static STAILQ_HEAD(, qentry)	queue = STAILQ_HEAD_INITIALIZER(queue);
-static unsigned long long	count;
+static long long		count;
 
 static struct qentry	*dequeue(void);
 

usr.bin/grep/util.c

@@ -196,11 +196,12 @@ int
 procfile(const char *fn)
 {
 	struct parsec pc;
+	long long tail;
 	struct file *f;
 	struct stat sb;
 	struct str *ln;
 	mode_t s;
-	int c, last_outed, t, tail;
+	int c, last_outed, t;
 	bool doctx, printmatch, same_file;
 
 	if (strcmp(fn, "-") == 0) {