On Mon, Jun 06, 2011 at 06:15:08AM +0100, Ben Hutchings wrote:
>This patch should provide the necessary kernel version check, but I
>haven't tested it.
>
>Ben.
>
>--- vsftpd-2.3.2.orig/sysdeputil.c
>+++ vsftpd-2.3.2/sysdeputil.c
>@@ -25,6 +25,11 @@
> #define _LARGEFILE64_SOURCE 1
> #endif
>
>+#ifdef __linux__
>+ #include <stdio.h>
>+ #include <sys/utsname.h>
>+#endif
>+
> /* For INT_MAX */
> #include <limits.h>
>
>@@ -1261,11 +1266,36 @@
> #endif
> }
>
>+#ifdef VSF_SYSDEP_HAVE_LINUX_CLONE
>+/* On Linux versions <2.6.35, netns cleanup may be so slow that
>+ * creating a netns per connection allows a remote denial-of-service.
>+ * We therefore do not use CLONE_NEWNET on these versions.
>+ */
>+static int
>+vsf_sysutil_netns_cleanup_is_fast(void)
>+{
>+#ifdef __linux__
>+ struct utsname utsname;
>+ int r1, r2, r3 = 0;
>+ return (uname(&utsname) == 0 &&
>+ sscanf(utsname.release, "%d.%d.%d", &r1, &r2, &r3) >= 2 &&
>+ ((r1 << 16) | (r2 << 8) | r3) >= ((2 << 16) | (6 << 8) | 35));
>+#else
>+ /* Assume any other kernel that has the feature don't have this problem */
>+ return 1;
>+#endif
>+}
>+#endif
>+
> int
> vsf_sysutil_fork_isolate_all_failok()
> {
> #ifdef VSF_SYSDEP_HAVE_LINUX_CLONE
>- static int cloneflags_work = 1;
>+ static int cloneflags_work = -1;
>+ if (cloneflags_work < 0)
>+ {
>+ cloneflags_work = vsf_sysutil_netns_cleanup_is_fast();
>+ }
> if (cloneflags_work)
> {
> int ret = syscall(__NR_clone,
>@@ -1311,7 +1341,11 @@
> vsf_sysutil_fork_newnet()
> {
> #ifdef VSF_SYSDEP_HAVE_LINUX_CLONE
>- static int cloneflags_work = 1;
>+ static int cloneflags_work = -1;
>+ if (cloneflags_work < 0)
>+ {
>+ cloneflags_work = vsf_sysutil_netns_cleanup_is_fast();
>+ }
> if (cloneflags_work)
> {
> int ret = syscall(__NR_clone, CLONE_NEWNET | SIGCHLD, NULL);
This simple patch seems to work just fine for me, and has stopped a
severe DOS here.
Daniel: any chance of a stable-security update for this please?
--
Steve McIntyre, Cambridge, UK. st...@einval.com
You raise the blade, you make the change... You re-arrange me 'til I'm sane...
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