[src/trunk]: src/usr.sbin/sysinst When reading output from a program we don't...

[martin <martin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/41c42d46d57c
branches:  trunk
changeset: 1022720:41c42d46d57c
user:      martin <martin%NetBSD.org@localhost>
date:      Tue Aug 03 13:34:04 2021 +0000

description:
When reading output from a program we don't know how much it will
be - so scale the buffer (within reasonable limits).
Problem pointed out by RVP, triggered e.g. by disks with lots of GPT
partitions.

diffstat:

 usr.sbin/sysinst/run.c |  41 +++++++++++++++++++++++++++++++++++------
 1 files changed, 35 insertions(+), 6 deletions(-)

diffs (90 lines):

diff -r 59e5591c2663 -r 41c42d46d57c usr.sbin/sysinst/run.c
--- a/usr.sbin/sysinst/run.c    Tue Aug 03 11:30:25 2021 +0000
+++ b/usr.sbin/sysinst/run.c    Tue Aug 03 13:34:04 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: run.c,v 1.13 2019/11/16 20:26:59 martin Exp $  */
+/*     $NetBSD: run.c,v 1.14 2021/08/03 13:34:04 martin Exp $  */
 
 /*
  * Copyright 1997 Piermont Information Systems Inc.
@@ -176,6 +176,7 @@
 {
        size_t nbytes;          /* Number of bytes in buffer. */
        size_t fbytes;          /* Number of bytes in file. */
+       size_t abytes;          /* allocated size of buffer */
        struct stat st;         /* stat information. */
        int ch;
        FILE *f;
@@ -198,6 +199,9 @@
                /* Open the file. */
                f = fopen(fileorcmd, "r");
                if (f == NULL) {
+                       if (logfp)
+                               fprintf(logfp, "%s: failed to open %s\n",
+                                   __func__, fileorcmd);
                        *buffer = NULL;
                        return -1;
                }
@@ -205,25 +209,47 @@
                /* Open the program. */
                f = popen(fileorcmd, "r");
                if (f == NULL) {
+                       if (logfp)
+                               fprintf(logfp, "%s: failed to open %s\n",
+                                   __func__, fileorcmd);
                        *buffer = NULL;
                        return -1;
                }
-               fbytes = BUFSIZE;
+               fbytes = 0;
        }
 
        if (fbytes == 0)
-               fbytes = BUFSIZE;
+               abytes = BUFSIZE;
+       else
+               abytes = fbytes+1;
 
        /* Allocate the buffer size. */
-       *buffer = cp = malloc(fbytes + 1);
+       *buffer = cp = malloc(abytes);
        if (!cp)
                nbytes =  -1;
        else {
                /* Read the buffer. */
                nbytes = 0;
-               while (nbytes < fbytes && (ch = fgetc(f)) != EOF)
+               while ((ch = fgetc(f)) != EOF) {
+                       if (nbytes >= abytes-1) {
+                               if (fbytes > 0 || abytes >= 512*BUFSIZE) {
+                                       free(cp);
+                                       *buffer = cp = NULL;
+                                       nbytes = -1;
+                                       break;
+                               }
+                               abytes *= 2;
+                               *buffer = cp = realloc(cp, abytes);
+                               if (!cp) {
+                                       nbytes =  -1;
+                                       break;
+                               }
+
+                       }
                        cp[nbytes++] = ch;
-               cp[nbytes] = 0;
+               }
+               if (cp)
+                       cp[nbytes] = 0;
        }
 
        if (kind == T_FILE)
@@ -231,6 +257,9 @@
        else
                pclose(f);
 
+       if (nbytes <= 0 && logfp)
+               fprintf(logfp, "%s: failed for %s\n", __func__, fileorcmd);
+
        return nbytes;
 }