nightmaremail

commit 129357b0a0eb10ec2b714ad198f63d9d016b8d59
parent 83e8e3215d2f664d6bb369562fcabb427fb18b5a
Author: Rolf Eike Beer <eike@sf-mail.de>
Date:   Fri,  6 Mar 2020 16:33:59 +0100

qmail-local: close race window when creating file in tmp/

The code checked if a file with the same name already exists and then tries to
create it. It properly checks if the latter fails and retries later, but this is
totally unnecessary: it could just try to create it, and handle it at this point
if the file already exists. This also saves one stat() syscall per local
delivery.

Diffstat:
M
qmail-local.c
 | 
20
+++++++++++---------

1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/qmail-local.c b/qmail-local.c
@@ -84,7 +84,6 @@ char *dir;
  char myhost[64];
  char *s;
  int loop;
- struct stat st;
  int fd;
  substdio ss;
  substdio ssout;
@@ -102,18 +101,21 @@ char *dir;
    s += fmt_ulong(s,time); *s++ = '.';
    s += fmt_ulong(s,pid); *s++ = '.';
    s += fmt_strn(s,myhost,sizeof(myhost)); *s++ = 0;
-   if (stat(fntmptph,&st) == -1) if (errno == error_noent) break;
-   /* really should never get to this point */
-   if (loop == 2) _exit(1);
-   sleep(2);
+   alarm(86400);
+   fd = open_excl(fntmptph);
+   if (fd >= 0)
+     break;
+   if (errno == error_exist) {
+     /* really should never get to this point */
+     if (loop == 2) _exit(1);
+     sleep(2);
+   } else {
+     _exit(1);
+   }
   }
  str_copy(fnnewtph,fntmptph);
  byte_copy(fnnewtph,3,"new");
 
- alarm(86400);
- fd = open_excl(fntmptph);
- if (fd == -1) _exit(1);
-
  substdio_fdbuf(&ss,read,0,buf,sizeof(buf));
  substdio_fdbuf(&ssout,write,fd,outbuf,sizeof(outbuf));
  if (substdio_put(&ssout,rpline.s,rpline.len) == -1) goto fail;