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Subject[PATCH 104/173] Prevent rt_sigqueueinfo and rt_tgsigqueueinfo from spoofing the signal code review patch.  If anyone has any objections, please let us know.


From: Julien Tinnes <>

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 <>
Acked-by: Oleg Nesterov <>
Signed-off-by: Linus Torvalds <>
Signed-off-by: Greg Kroah-Hartman <>
[wt: 2.6.27 does not have do_rt_tgsigqueueinfo()]

kernel/signal.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

Index: longterm-2.6.27/kernel/signal.c
--- longterm-2.6.27.orig/kernel/signal.c 2011-01-23 10:52:37.000000000 +0100
+++ longterm-2.6.27/kernel/signal.c 2011-04-25 16:06:27.491278774 +0200
@@ -2294,9 +2294,13 @@
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. */

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