From 66dd34ad31e5963d72a700ec3f2449291d322921 Mon Sep 17 00:00:00 2001 From: Andrey Vagin Date: Wed, 27 Feb 2013 17:03:12 -0800 Subject: [PATCH] signal: allow to send any siginfo to itself The idea is simple. We need to get the siginfo for each signal on checkpointing dump, and then return it back on restore. The first problem is that the kernel doesn't report complete siginfos to userspace. In a signal handler the kernel strips SI_CODE from siginfo. When a siginfo is received from signalfd, it has a different format with fixed sizes of fields. The interface of signalfd was extended. If a signalfd is created with the flag SFD_RAW, it returns siginfo in a raw format. rt_sigqueueinfo looks suitable for restoring signals, but it can't send siginfo with a positive si_code, because these codes are reserved for the kernel. In the real world each person has right to do anything with himself, so I think a process should able to send any siginfo to itself. This patch: The kernel prevents sending of siginfo with positive si_code, because these codes are reserved for kernel. I think we can allow a task to send such a siginfo to itself. This operation should not be dangerous. This functionality is required for restoring signals in checkpoint/restart. Signed-off-by: Andrey Vagin Cc: Serge Hallyn Cc: "Eric W. Biederman" Cc: Al Viro Cc: Michael Kerrisk Cc: Pavel Emelyanov Cc: Cyrill Gorcunov Cc: Michael Kerrisk Reviewed-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index 2a7ae2963185..c6209135cca4 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2996,7 +2996,8 @@ 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 ((info->si_code >= 0 || info->si_code == SI_TKILL) && + (task_pid_vnr(current) != pid)) { /* We used to allow any < 0 si_code */ WARN_ON_ONCE(info->si_code < 0); return -EPERM; @@ -3045,7 +3046,8 @@ 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 (((info->si_code >= 0 || info->si_code == SI_TKILL)) && + (task_pid_vnr(current) != pid)) { /* We used to allow any < 0 si_code */ WARN_ON_ONCE(info->si_code < 0); return -EPERM; -- 2.20.1