0055-vsf_sysutil_get_tz-Check-the-return-value-of-syscall.patch

From c7ac05fdf2a7b53d901bfc3afeb9a61916aaaaf1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Lyson=C4=9Bk?= <olysonek@redhat.com>
Date: Wed, 9 May 2018 20:26:37 +0200
Subject: [PATCH 55/59] vsf_sysutil_get_tz: Check the return value of syscalls

Check the return value of syscalls. There's always the possibility that
they'll fail. (Failure of close() is not handled though, apart from EINTR.
The file is open read-only so it shouldn't fail, and even if it does,
it's not tragic.)

We return NULL in case of syscall failure. One might be tempted to simply
call die() when any kind of error occurs when parsing the timezone data,
but I think it's more in line with the behaviour of tzset(3) not to do
anything drastic in such a case (tzset() will silently use UTC when
the value given in the TZ environment variable is invalid).
---
 sysutil.c | 46 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 37 insertions(+), 9 deletions(-)

diff --git a/sysutil.c b/sysutil.c
index de5f876..fd07d99 100644
--- a/sysutil.c
+++ b/sysutil.c
@@ -2647,12 +2647,12 @@ error:
   die("reopening standard file descriptors to /dev/null failed");
 }
 
-char* vsf_sysutil_get_tz()
+char* vsf_sysutil_get_tz(void)
 {
   char *ret_tz = NULL;
   char buff[BUFTZSIZ];
   off_t s_pos, e_pos;
-  size_t rcnt, rest;
+  ssize_t rcnt, rest;
   int fd;
 
   if ((fd = open(F_LOCALTIME, O_RDONLY)) > -1)
@@ -2663,8 +2663,12 @@ char* vsf_sysutil_get_tz()
       return NULL;
     }
     s_pos = e_pos > BUFTZSIZ ? e_pos - BUFTZSIZ : 0;
-    lseek(fd, s_pos, SEEK_SET);
-    rcnt = read(fd, buff, BUFTZSIZ);
+    if (lseek(fd, s_pos, SEEK_SET) == -1 ||
+        (rcnt = vsf_sysutil_read(fd, buff, BUFTZSIZ)) == -1)
+    {
+      close(fd);
+      return NULL;
+    }
 
     if (rcnt && buff[rcnt-1] == '\n')
     {
@@ -2680,10 +2684,25 @@ char* vsf_sysutil_get_tz()
          int len = e_pos - s_pos - offset;
          if (len)
          {
-           lseek(fd, s_pos + offset, SEEK_SET);
+           if (lseek(fd, s_pos + offset, SEEK_SET) == -1)
+           {
+             close(fd);
+             return NULL;
+           }
            ret_tz = calloc(1, len+4);
+           if (ret_tz == NULL)
+           {
+             close(fd);
+             return NULL;
+           }
            memcpy(ret_tz, "TZ=", 3);
-           rcnt = read(fd, ret_tz+3, len);
+           rcnt = vsf_sysutil_read(fd, ret_tz+3, len);
+           if (rcnt == -1)
+           {
+             free(ret_tz);
+             close(fd);
+             return NULL;
+           }
          }
          break;
        }
@@ -2693,11 +2712,20 @@ char* vsf_sysutil_get_tz()
        }
        rest = s_pos > BUFTZSIZ ? s_pos - BUFTZSIZ : 0;
        s_pos -= rest;
-       lseek(fd, s_pos, SEEK_SET);
-       rcnt = read(fd, buff, rest);
+       if (lseek(fd, s_pos, SEEK_SET) == -1)
+       {
+         close(fd);
+         return NULL;
+       }
+       rcnt = vsf_sysutil_read(fd, buff, rest);
+       if (rcnt == -1)
+       {
+         close(fd);
+         return NULL;
+       }
     } while (rcnt > 0);
 
-    close (fd);
+    (void) vsf_sysutil_close_errno(fd);
   }
 
   return ret_tz;
-- 
2.14.4