Re: Why fstat() in qmail-send.c:markdone()?
Fred Lindberg writes: It's obviously important or it wouldn't be there. It's a variable that was used with the original qmail queue structure. It's unused now, and can be removed safely. ---Dan
Re: Why fstat() in qmail-send.c:markdone()?
On Fri, 10 Mar 2000 14:42:15 -0600, Fred Lindberg wrote:
fd = open_write(fn.s);
if (fd == -1) break;
if (fstat(fd,st) == -1) { close(fd); break; }
if (seek_set(fd,pos) == -1) { close(fd); break; }
Ok, I get it. qmail-send doesn't trust qmailq. Without the fstat()
call, qmailq could (via symlink) cause qmail-send (root) to write to an
arbitrary location. fstat() should be faster and more portable than
temporarily dropping privileges(?).
-Sincerely, Fred
(Frederik Lindberg, Infectious Diseases, WashU, St. Louis, MO, USA)
Re: Why fstat() in qmail-send.c:markdone()?
"Fred Lindberg" [EMAIL PROTECTED] wrote: call, qmailq could (via symlink) cause qmail-send (root) to write to an qmail-send runs as qmails, not root. -Dave
Re: Why fstat() in qmail-send.c:markdone()?
On Wed, 15 Mar 2000 11:59:11 -0500 (EST), Dave Sill wrote: qmail-send runs as qmails, not root. Yes. And the file in question is owned by qmails not qmailq in a directory writable only by qmails. If open fails to report an error, this should become obvious in write(). The fstat() info is not used, but if only qmails can create a symlink and qmail-send runs as qmails, we're back to the original question: Why is the fstat() there? -Sincerely, Fred (Frederik Lindberg, Infectious Diseases, WashU, St. Louis, MO, USA)
Why fstat() in qmail-send.c:markdone()?
It's obviously important or it wouldn't be there. Can anyone explain
why?
From qmail-send.c: markdone():
for (;;)
{
fd = open_write(fn.s);
if (fd == -1) break;
if (fstat(fd,st) == -1) { close(fd); break; }
if (seek_set(fd,pos) == -1) { close(fd); break; }
if (write(fd,"D",1) != 1) { close(fd); break; }
/* further errors - double delivery without us knowing about it, oh
well */
close(fd);
return;
}
Thanks!
-Sincerely, Fred
(Frederik Lindberg, Infectious Diseases, WashU, St. Louis, MO, USA)
Re: Why fstat() in qmail-send.c:markdone()?
"Fred Lindberg" [EMAIL PROTECTED] wrote: It's obviously important or it wouldn't be there. Can anyone explain why? Forgive my speculation--if I'm wrong, somebody correct me! My guess is that fstat() follows open() because of system-specific open() bugs. On NFS, for example, open() will sometimes return a descriptor, but subsequent write() calls will fail with EACCESS. This condition can be detected through error slippage by calling fstat(), which will also fail with EACCESS. Len. -- The whole point of modern `standards' is to preserve the existing oligopoly. A few vendors band together to produce a `standard' that is precisely the disjoint union of their existing implementations, including all their warts. -- Henry Baker
