rt_sigqueueinfo and rt_tgsigqueueinfo check the value of si_code to
prevent a process from spoofing a kernel-generated signal or one
generated by kill/tgkill.
Unfortunately this check failed to take into account the fact that
the si_code value seen by a user process is only the low 16 bits of
the value in the kernel. It was still possible to spoof any si_code
by ORing 0xffff into the top 16 bits.
The check is tightened by checking the value of si_code that will
be seen by a user program instead of the one in the kernel.
Signed-off-by: Amanieu d'Antras <aman...@gmail.com>
---
kernel/signal.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c
index 0f6bbbe..f3d4f39 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2989,7 +2989,7 @@ static int do_rt_sigqueueinfo(pid_t pid, int sig,
siginfo_t *info)
/* Not even root can pretend to send signals from the kernel.
* Nor can they impersonate a kill()/tgkill(), which adds source info.
*/
- if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
+ if (((short)info->si_code >= 0 || (short)info->si_code == SI_TKILL) &&
(task_pid_vnr(current) != pid))
return -EPERM;
@@ -3037,7 +3037,7 @@ static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid,
int sig, siginfo_t *info)
/* Not even root can pretend to send signals from the kernel.
* Nor can they impersonate a kill()/tgkill(), which adds source info.
*/
- if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
+ if (((short)info->si_code >= 0 || (short)info->si_code == SI_TKILL) &&
(task_pid_vnr(current) != pid))
return -EPERM;
--
2.6.1
--
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