[glibc] Fix off-by-one OOB write in iconv/tst-iconv-mt

[glibc] Fix off-by-one OOB write in iconv/tst-iconv-mt

[Szabolcs Nagy]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=0a520f28ffc8820d46074a71323db4c9652873be

commit 0a520f28ffc8820d46074a71323db4c9652873be
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Mon Sep 26 15:38:19 2022 +0100

    Fix off-by-one OOB write in iconv/tst-iconv-mt
    
    The iconv buffer sizes must not include the \0 string terminator.
    And the output termination with *outbufpos = '\0' was OOB.
    
    Consistently use non-null-terminated buffer sizes.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 iconv/tst-iconv-mt.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/iconv/tst-iconv-mt.c b/iconv/tst-iconv-mt.c
index e634eec1b7..8d7867b323 100644
--- a/iconv/tst-iconv-mt.c
+++ b/iconv/tst-iconv-mt.c
@@ -57,12 +57,13 @@ worker (void * arg)
   iconv_t cd;
 
   char ascii[] = CONV_INPUT;
+  size_t bytes = sizeof (CONV_INPUT) - 1;
   char *inbufpos = ascii;
-  size_t inbytesleft = sizeof (CONV_INPUT);
+  size_t inbytesleft = bytes;
 
-  char *utf8 = xcalloc (sizeof (CONV_INPUT), 1);
+  char *utf8 = xcalloc (bytes, 1);
   char *outbufpos = utf8;
-  size_t outbytesleft = sizeof (CONV_INPUT);
+  size_t outbytesleft = bytes;
 
   if (tidx < TCOUNT/2)
     /* The first half of the worker thread pool synchronize together here,
@@ -91,8 +92,6 @@ worker (void * arg)
                            &outbytesleft)
                     != (size_t) -1);
 
-  *outbufpos = '\0';
-
   xpthread_barrier_wait (&sync);
 
   TEST_VERIFY_EXIT (iconv_close (cd) == 0);
@@ -104,11 +103,7 @@ worker (void * arg)
   if (tidx < TCOUNT/2)
     xpthread_barrier_wait (&sync);
 
-  if (strncmp (utf8, CONV_INPUT, sizeof CONV_INPUT))
-    {
-      printf ("FAIL: thread %lx: invalid conversion output from iconv\n", tidx);
-      pthread_exit ((void *) (long int) 1);
-    }
+  TEST_COMPARE_BLOB (utf8, bytes, CONV_INPUT, bytes);
 
   pthread_exit (NULL);
 }