[glibc] Fix subscript error with odd TZif file [BZ #28338]

[glibc] Fix subscript error with odd TZif file [BZ #28338]

[Adhemerval Zanella]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=645277434a42efc547d2cac8bfede4da10b4049f

commit 645277434a42efc547d2cac8bfede4da10b4049f
Author: Paul Eggert <eggert@cs.ucla.edu>
Date:   Mon Sep 13 22:49:45 2021 -0700

    Fix subscript error with odd TZif file [BZ #28338]
    
    * time/tzfile.c (__tzfile_compute): Fix unlikely off-by-one bug
    that accessed before start of an array when an oddball-but-valid
    TZif file was queried with an unusual time_t value.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 time/tzfile.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/time/tzfile.c b/time/tzfile.c
index 4377018a55..190a777152 100644
--- a/time/tzfile.c
+++ b/time/tzfile.c
@@ -765,8 +765,7 @@ __tzfile_compute (__time64_t timer, int use_localtime,
   *leap_correct = leaps[i].change;
 
   if (timer == leaps[i].transition /* Exactly at the transition time.  */
-      && ((i == 0 && leaps[i].change > 0)
-	  || leaps[i].change > leaps[i - 1].change))
+      && (leaps[i].change > (i == 0 ? 0 : leaps[i - 1].change)))
     {
       *leap_hit = 1;
       while (i > 0