From: Julien Tinnes Date: Fri, 18 Mar 2011 22:05:21 +0000 (-0700) Subject: Prevent rt_sigqueueinfo and rt_tgsigqueueinfo from spoofing the signal code X-Git-Tag: firefly_0821_release~7613^2~2123 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=da48524eb206;p=firefly-linux-kernel-4.4.55.git Prevent rt_sigqueueinfo and rt_tgsigqueueinfo from spoofing the signal code 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 Acked-by: Oleg Nesterov Signed-off-by: Linus Torvalds --- diff --git a/kernel/signal.c b/kernel/signal.c index 4e3cff10fdce..31751868de88 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2421,9 +2421,13 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig, 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, pid_t pid, int sig, siginfo_t *info) 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);