From: Oleg Nesterov oleg@redhat.com Subject: ipc/mqueue.c: change __do_notify() to bypass check_kill_permission()

Commit cc731525f26a ("signal: Remove kernel interal si_code magic") changed the value of SI_FROMUSER(SI_MESGQ), this means that mq_notify() no longer works if the sender doesn't have rights to send a signal.

Change __do_notify() to use do_send_sig_info() instead of kill_pid_info() to avoid check_kill_permission().

This needs the additional notify.sigev_signo != 0 check, shouldn't we change do_mq_notify() to deny sigev_signo == 0 ?

Test-case:

#include <signal.h> #include <mqueue.h> #include <unistd.h> #include <sys/wait.h> #include <assert.h>

static int notified;

static void sigh(int sig) { notified = 1; }

int main(void) { signal(SIGIO, sigh);

int fd = mq_open("/mq", O_RDWR|O_CREAT, 0666, NULL); assert(fd >= 0);

struct sigevent se = { .sigev_notify = SIGEV_SIGNAL, .sigev_signo = SIGIO, }; assert(mq_notify(fd, &se) == 0);

if (!fork()) { assert(setuid(1) == 0); mq_send(fd, "",1,0); return 0; }

wait(NULL); mq_unlink("/mq"); assert(notified); return 0; }

[manfred@colorfullife.com: 1) Add self_exec_id evaluation so that the implementation matches do_notify_parent 2) use PIDTYPE_TGID everywhere] Link: http://lkml.kernel.org/r/e2a782e4-eab9-4f5c-c749-c07a8f7a4e66@colorfullife.c... Fixes: cc731525f26a ("signal: Remove kernel interal si_code magic") Reported-by: Yoji yoji.fujihar.min@gmail.com Signed-off-by: Oleg Nesterov oleg@redhat.com Signed-off-by: Manfred Spraul manfred@colorfullife.com Acked-by: "Eric W. Biederman" ebiederm@xmission.com Cc: Davidlohr Bueso dave@stgolabs.net Cc: Markus Elfring elfring@users.sourceforge.net Cc: 1vier1@web.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

ipc/mqueue.c | 34 ++++++++++++++++++++++++++-------- 1 file changed, 26 insertions(+), 8 deletions(-)

--- a/ipc/mqueue.c~ipc-mqueuec-change-__do_notify-to-bypass-check_kill_permission-v2 +++ a/ipc/mqueue.c @@ -142,6 +142,7 @@ struct mqueue_inode_info {

struct sigevent notify; struct pid *notify_owner; + u32 notify_self_exec_id; struct user_namespace *notify_user_ns; struct user_struct *user; /* user who created, for accounting */ struct sock *notify_sock; @@ -773,28 +774,44 @@ static void __do_notify(struct mqueue_in * synchronously. */ if (info->notify_owner && info->attr.mq_curmsgs == 1) { - struct kernel_siginfo sig_i; switch (info->notify.sigev_notify) { case SIGEV_NONE: break; - case SIGEV_SIGNAL: - /* sends signal */ + case SIGEV_SIGNAL: { + struct kernel_siginfo sig_i; + struct task_struct *task; + + /* do_mq_notify() accepts sigev_signo == 0, why?? */ + if (!info->notify.sigev_signo) + break;

clear_siginfo(&sig_i); sig_i.si_signo = info->notify.sigev_signo; sig_i.si_errno = 0; sig_i.si_code = SI_MESGQ; sig_i.si_value = info->notify.sigev_value; - /* map current pid/uid into info->owner's namespaces */ rcu_read_lock(); + /* map current pid/uid into info->owner's namespaces */ sig_i.si_pid = task_tgid_nr_ns(current, ns_of_pid(info->notify_owner)); - sig_i.si_uid = from_kuid_munged(info->notify_user_ns, current_uid()); + sig_i.si_uid = from_kuid_munged(info->notify_user_ns, + current_uid()); + /* + * We can't use kill_pid_info(), this signal should + * bypass check_kill_permission(). It is from kernel + * but si_fromuser() can't know this. + * We do check the self_exec_id, to avoid sending + * signals to programs that don't expect them. + */ + task = pid_task(info->notify_owner, PIDTYPE_TGID); + if (task && task->self_exec_id == + info->notify_self_exec_id) { + do_send_sig_info(info->notify.sigev_signo, + &sig_i, task, PIDTYPE_TGID); + } rcu_read_unlock(); - - kill_pid_info(info->notify.sigev_signo, - &sig_i, info->notify_owner); break; + } case SIGEV_THREAD: set_cookie(info->notify_cookie, NOTIFY_WOKENUP); netlink_sendskb(info->notify_sock, info->notify_cookie); @@ -1383,6 +1400,7 @@ retry: info->notify.sigev_signo = notification->sigev_signo; info->notify.sigev_value = notification->sigev_value; info->notify.sigev_notify = SIGEV_SIGNAL; + info->notify_self_exec_id = current->self_exec_id; break; }

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