From: Eric Blake <eblake@redhat.com>
To: cygwin-patches@cygwin.com
Subject: fix off-by-one in dup2
Date: Wed, 25 Sep 2013 23:26:00 -0000 [thread overview]
Message-ID: <52437121.1070507@redhat.com> (raw)
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Solves the segfault here: http://cygwin.com/ml/cygwin/2013-09/msg00397.html
but does not address the fact that we are still screwy with regards to
rlimit.
======
Ultimately, based on my understanding of POSIX and glibc, my goal is to
have a number of changes (this patch only scratches the surface; there's
more to go):
dtable.h tracks soft and hard limits, inherited over fork and preserved
across exec
hard limit starts at OPEN_MAX_MAX and can only be reduced
soft limit starts at hard limit, and can be reduced to _POSIX_OPEN_MAX (8)
dtable.size starts at MAX(32, fork/exec size)
getdtablesize() and sysconf(_SC_OPEN_MAX) always returns the soft limit,
as in glibc and permitted by POSIX (_SC_OPEN_MAX is the only sysconf
variable that can be runtime dynamic)
dtable.size is decoupled from soft limit, and is guaranteed to be <=
hard limit. It can grow up to current soft limit; but soft limit can
later be reduced lower than dtable.size (glibc does this); on fork and
exec, we are careful to still allow fds beyond the current soft limit.
getrlimit(RLIMIT_NOFILE, &r) => returns soft and hard limits from dtable
rather than hard limit as a constant and soft limit as current dtable.size
setrlimit(RLIMIT_NOFILE, &r) => cannot set hard limit to unlimited; soft
limit of unlimited is translated to current hard limit; hard limit
cannot be increased (EPERM) or reduced below dtable.size (EINVAL); soft
limit can be reduced arbitrarily (including below OPEN_MAX of 256)
setdtablesize() => guarantees that dtable.size is at least that large
(must be <= soft limit), but does not lower dtable.size or change limits
=====
2013-09-25 Eric Blake <eblake@redhat.com>
dup2: fix off-by-one crash
* dtable.cc (dup3): Fix off-by-one.
(find_unused_handle): Reduce time spent expanding during dup.
* syscalls.cc (setdtablesize): Report error on invalid value.
diff --git i/winsup/cygwin/dtable.cc w/winsup/cygwin/dtable.cc
index 2501a26..c2982a8 100644
--- i/winsup/cygwin/dtable.cc
+++ w/winsup/cygwin/dtable.cc
@@ -233,7 +233,7 @@ dtable::find_unused_handle (int start)
if (fds[i] == NULL)
return i;
}
- while (extend (NOFILE_INCR));
+ while (extend (MAX (NOFILE_INCR, start - size)));
return -1;
}
@@ -754,7 +754,7 @@ dtable::dup3 (int oldfd, int newfd, int flags)
if (!not_open (newfd))
close (newfd);
- else if ((size_t) newfd > size
+ else if ((size_t) newfd >= size
&& find_unused_handle (newfd) < 0)
/* couldn't extend fdtab */
{
diff --git i/winsup/cygwin/syscalls.cc w/winsup/cygwin/syscalls.cc
index e1886e6..8c1c70a 100644
--- i/winsup/cygwin/syscalls.cc
+++ w/winsup/cygwin/syscalls.cc
@@ -2578,6 +2578,9 @@ system (const char *cmdstring)
extern "C" int
setdtablesize (int size)
{
+ if (size < 0)
+ return -1;
+
if (size <= (int)cygheap->fdtab.size || cygheap->fdtab.extend (size -
cygheap->fdtab.size))
return 0;
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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next reply other threads:[~2013-09-25 23:26 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-25 23:26 Eric Blake [this message]
2013-10-15 14:06 ` Christopher Faylor
2013-10-15 20:45 ` Yaakov (Cygwin/X)
2013-10-15 22:34 ` Christopher Faylor
2013-10-16 7:40 ` Yaakov (Cygwin/X)
2013-11-23 13:19 ` Eric Blake
2013-12-04 9:32 ` Corinna Vinschen
2013-12-04 11:36 ` Corinna Vinschen
2013-12-04 12:04 ` Corinna Vinschen
2013-12-04 17:00 ` Christopher Faylor
2013-12-04 17:23 ` Corinna Vinschen
2013-12-04 17:51 ` Christopher Faylor
2013-12-04 19:44 ` Corinna Vinschen
2013-12-05 13:45 ` Eric Blake
2013-12-05 19:56 ` Christopher Faylor
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