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authorJulien Tinnes <jln@google.com>2011-03-18 15:05:21 -0700
committerPaul Gortmaker <paul.gortmaker@windriver.com>2011-04-17 16:16:17 -0400
commit9eab773eb3eda5d8336a8f0ac68c5e1faa5f88d5 (patch)
tree5e52a82110c71363710603b85b1e96dd240c7a5e /kernel
parentc95610ef5cf44dcef45434ca6de0832aa9b02708 (diff)
Prevent rt_sigqueueinfo and rt_tgsigqueueinfo from spoofing the signal code
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: Paul Gortmaker <paul.gortmaker@windriver.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/signal.c16
1 files changed, 12 insertions, 4 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index edabc2f910bc..704c03089f2d 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2409,9 +2409,13 @@ 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. */
@@ -2425,9 +2429,13 @@ 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);