Commit 66dd34ad authored by Andrey Vagin's avatar Andrey Vagin Committed by Linus Torvalds

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: default avatarAndrey Vagin <avagin@openvz.org>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 52b233c8
...@@ -2996,7 +2996,8 @@ static int do_rt_sigqueueinfo(pid_t pid, int sig, siginfo_t *info) ...@@ -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. /* Not even root can pretend to send signals from the kernel.
* Nor can they impersonate a kill()/tgkill(), which adds source info. * 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 */ /* We used to allow any < 0 si_code */
WARN_ON_ONCE(info->si_code < 0); WARN_ON_ONCE(info->si_code < 0);
return -EPERM; return -EPERM;
...@@ -3045,7 +3046,8 @@ static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info) ...@@ -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. /* Not even root can pretend to send signals from the kernel.
* Nor can they impersonate a kill()/tgkill(), which adds source info. * 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 */ /* We used to allow any < 0 si_code */
WARN_ON_ONCE(info->si_code < 0); WARN_ON_ONCE(info->si_code < 0);
return -EPERM; return -EPERM;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment