[glibc] time: Fix use-after-free in getdate

[glibc] time: Fix use-after-free in getdate

[Arjun Shankar]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=85e6d8b4175fcb195011a0a1bad37d6f3b2355db

commit 85e6d8b4175fcb195011a0a1bad37d6f3b2355db
Author: Arjun Shankar <arjun@redhat.com>
Date:   Tue Jun 6 19:20:31 2023 +0200

    time: Fix use-after-free in getdate
    
    getdate would free the buffer pointed to by the result of its call to
    strptime, then reference the same buffer later on -- leading to a
    use-after-free.  This commit fixes that.
    
    Reported-by: Martin Coufal <mcoufal@redhat.com>
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 time/getdate.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/time/getdate.c b/time/getdate.c
index 1dcbd77188..ca058394a3 100644
--- a/time/getdate.c
+++ b/time/getdate.c
@@ -114,6 +114,7 @@ __getdate_r (const char *string, struct tm *tp)
   struct tm tm;
   struct __stat64_t64 st;
   bool mday_ok = false;
+  bool found = false;
 
   datemsk = getenv ("DATEMSK");
   if (datemsk == NULL || *datemsk == '\0')
@@ -181,7 +182,7 @@ __getdate_r (const char *string, struct tm *tp)
       tp->tm_gmtoff = 0;
       tp->tm_zone = NULL;
       result = strptime (string, line, tp);
-      if (result && *result == '\0')
+      if ((found = (result && *result == '\0')))
 	break;
     }
   while (!__feof_unlocked (fp));
@@ -201,7 +202,7 @@ __getdate_r (const char *string, struct tm *tp)
   /* Close template file.  */
   fclose (fp);
 
-  if (result == NULL || *result != '\0')
+  if (!found)
     return 7;
 
   /* Get current time.  */