On Tue, 17 Jul 2018 13:21:31 -0600, "Todd C. Miller" wrote:

> It probably makes more sense to do the newline check (and decrement
> len if one is present) before newsize is computed.  Then you would
> need to unconditionally NUL-terminate lp->line.

Perhaps something like this.

 - todd

Index: usr.bin/join/join.c
===================================================================
RCS file: /cvs/src/usr.bin/join/join.c,v
retrieving revision 1.27
diff -u -p -u -r1.27 join.c
--- usr.bin/join/join.c 9 Oct 2015 01:37:07 -0000       1.27
+++ usr.bin/join/join.c 17 Jul 2018 19:33:38 -0000
@@ -298,9 +298,10 @@ void
 slurpit(INPUT *F)
 {
        LINE *lp, *lastlp, tmp;
-       size_t len;
+       ssize_t len;
+       size_t linesize;
        u_long cnt;
-       char *bp, *fieldp;
+       char *bp, *fieldp, *line;
        long fpos;
        /*
         * Read all of the lines from an input file that have the same
@@ -308,6 +309,8 @@ slurpit(INPUT *F)
         */
 
        F->setcnt = 0;
+       line = NULL;
+       linesize = 0;
        for (lastlp = NULL; ; ++F->setcnt, lastlp = lp) {
                /*
                 * If we're out of space to hold line structures, allocate
@@ -343,13 +346,19 @@ slurpit(INPUT *F)
                        F->pushbool = 0;
                        continue;
                }
-               if ((bp = fgetln(F->fp, &len)) == NULL)
+               if ((len = getline(&line, &linesize, F->fp)) == -1) {
+                       free(line);
                        return;
+               }
                /*
                 * we depend on knowing on what field we are, one safe way is
                 * the file position.
                */
                fpos = ftell(F->fp) - len;
+
+               /* Remove trailing newline, if it exists, and copy line. */
+               if (line[len - 1] == '\n')
+                       len--;
                if (lp->linealloc <= len + 1) {
                        char *p;
                        u_long newsize = lp->linealloc +
@@ -360,17 +369,13 @@ slurpit(INPUT *F)
                        lp->linealloc = newsize;
                }
                F->setusedc++;
-               memmove(lp->line, bp, len);
+               memcpy(lp->line, line, len);
+               lp->line[len] = '\0';
                lp->fpos = fpos;
-               /* Replace trailing newline, if it exists. */
-               if (bp[len - 1] == '\n')
-                       lp->line[len - 1] = '\0';
-               else
-                       lp->line[len] = '\0';
-               bp = lp->line;
 
                /* Split the line into fields, allocate space as necessary. */
                lp->fieldcnt = 0;
+               bp = lp->line;
                while ((fieldp = strsep(&bp, tabchar)) != NULL) {
                        if (spans && *fieldp == '\0')
                                continue;
@@ -393,6 +398,7 @@ slurpit(INPUT *F)
                        break;
                }
        }
+       free(line);
 }
 
 int

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