Messages in this thread Patch in this message | | | Date | Fri, 25 Mar 2011 16:43:58 -0700 | From | Greg KH <> | Subject | [22/63] Prevent rt_sigqueueinfo and rt_tgsigqueueinfo from spoofing the signal code |
| |
2.6.38-stable review patch. If anyone has any objections, please let us know.
------------------
From: Julien Tinnes <jln@google.com>
commit da48524eb20662618854bb3df2db01fc65f3070c upstream.
Userland should be able to trust the pid and uid of the sender of a signal if the si_code is SI_TKILL.
Unfortunately, the kernel has historically allowed sigqueueinfo() to send any si_code at all (as long as it was negative - to distinguish it from kernel-generated signals like SIGILL etc), so it could spoof a SI_TKILL with incorrect siginfo values.
Happily, it looks like glibc has always set si_code to the appropriate SI_QUEUE, so there are probably no actual user code that ever uses anything but the appropriate SI_QUEUE flag.
So just tighten the check for si_code (we used to allow any negative value), and add a (one-time) warning in case there are binaries out there that might depend on using other si_code values.
Signed-off-by: Julien Tinnes <jln@google.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- kernel/signal.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)
--- a/kernel/signal.c +++ b/kernel/signal.c @@ -2421,9 +2421,13 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, return -EFAULT; /* Not even root can pretend to send signals from the kernel. - Nor can they impersonate a kill(), which adds source info. */ - if (info.si_code >= 0) + * Nor can they impersonate a kill()/tgkill(), which adds source info. + */ + if (info.si_code != SI_QUEUE) { + /* We used to allow any < 0 si_code */ + WARN_ON_ONCE(info.si_code < 0); return -EPERM; + } info.si_signo = sig; /* POSIX.1b doesn't mention process groups. */ @@ -2437,9 +2441,13 @@ long do_rt_tgsigqueueinfo(pid_t tgid, pi return -EINVAL; /* Not even root can pretend to send signals from the kernel. - Nor can they impersonate a kill(), which adds source info. */ - if (info->si_code >= 0) + * Nor can they impersonate a kill()/tgkill(), which adds source info. + */ + if (info->si_code != SI_QUEUE) { + /* We used to allow any < 0 si_code */ + WARN_ON_ONCE(info->si_code < 0); return -EPERM; + } info->si_signo = sig; return do_send_specific(tgid, pid, sig, info);
| |