Messages in this thread Patch in this message | | | From | Amanieu d'Antras <> | Subject | [PATCH] signal: Make the si_code check in rt_[tg]sigqueueinfo stricter | Date | Mon, 12 Oct 2015 16:33:54 +0100 |
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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 <amanieu@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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