2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Julien Tinnes <[email protected]> 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 <[email protected]> Acked-by: Oleg Nesterov <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> Signed-off-by: Andi Kleen <[email protected]> --- kernel/signal.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) Index: linux-2.6.35.y/kernel/signal.c =================================================================== --- linux-2.6.35.y.orig/kernel/signal.c 2011-03-29 22:50:25.616602954 -0700 +++ linux-2.6.35.y/kernel/signal.c 2011-03-29 23:03:02.941224912 -0700 @@ -2410,9 +2410,13 @@ 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. */ @@ -2426,9 +2430,13 @@ 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); _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
