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Commit faf1f22b authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

signal: Ensure generic siginfos the kernel sends have all bits initialized 



Call clear_siginfo to ensure stack allocated siginfos are fully
initialized before being passed to the signal sending functions.

This ensures that if there is the kind of confusion documented by
TRAP_FIXME, FPE_FIXME, or BUS_FIXME the kernel won't send unitialized
data to userspace when the kernel generates a signal with SI_USER but
the copy to userspace assumes it is a different kind of signal, and
different fields are initialized.

This also prepares the way for turning copy_siginfo_to_user
into a copy_to_user, by removing the need in many cases to perform
a field by field copy simply to skip the uninitialized fields.

Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 8c5dbf2a

fs/fcntl.c

+1 −0
Original line number Diff line number Diff line
@@ -737,6 +737,7 @@ static void send_sigio_to_task(struct task_struct *p, 
			   delivered even if we can't queue.  Failure to

			   queue in this case _should_ be reported; we fall

			   back to SIGIO in that case. --sct */

			clear_siginfo(&si);

			si.si_signo = signum;

			si.si_errno = 0;

		        si.si_code  = reason;

ipc/mqueue.c

+1 −0
Original line number Diff line number Diff line
@@ -639,6 +639,7 @@ static void __do_notify(struct mqueue_inode_info *info) 
		case SIGEV_SIGNAL:

			/* sends signal */



			clear_siginfo(&sig_i);

			sig_i.si_signo = info->notify.sigev_signo;

			sig_i.si_errno = 0;

			sig_i.si_code = SI_MESGQ;

kernel/signal.c

+8 −1
Original line number Diff line number Diff line
@@ -549,6 +549,7 @@ static void collect_signal(int sig, struct sigpending *list, siginfo_t *info, 
		 * a fast-pathed signal or we must have been

		 * out of queue space.  So zero out the info.

		 */

		clear_siginfo(info);

		info->si_signo = sig;

		info->si_errno = 0;

		info->si_code = SI_USER;
@@ -1043,6 +1044,7 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t, 
		list_add_tail(&q->list, &pending->list);

		switch ((unsigned long) info) {

		case (unsigned long) SEND_SIG_NOINFO:

			clear_siginfo(&q->info);

			q->info.si_signo = sig;

			q->info.si_errno = 0;

			q->info.si_code = SI_USER;
@@ -1051,6 +1053,7 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t, 
			q->info.si_uid = from_kuid_munged(current_user_ns(), current_uid());

			break;

		case (unsigned long) SEND_SIG_PRIV:

			clear_siginfo(&q->info);

			q->info.si_signo = sig;

			q->info.si_errno = 0;

			q->info.si_code = SI_KERNEL;
@@ -1623,6 +1626,7 @@ bool do_notify_parent(struct task_struct *tsk, int sig) 
			sig = SIGCHLD;

	}



	clear_siginfo(&info);

	info.si_signo = sig;

	info.si_errno = 0;

	/*
@@ -1717,6 +1721,7 @@ static void do_notify_parent_cldstop(struct task_struct *tsk, 
		parent = tsk->real_parent;

	}



	clear_siginfo(&info);

	info.si_signo = SIGCHLD;

	info.si_errno = 0;

	/*
@@ -1929,7 +1934,7 @@ static void ptrace_do_notify(int signr, int exit_code, int why) 
{

	siginfo_t info;



	memset(&info, 0, sizeof info);

	clear_siginfo(&info);

	info.si_signo = signr;

	info.si_code = exit_code;

	info.si_pid = task_pid_vnr(current);
@@ -2136,6 +2141,7 @@ static int ptrace_signal(int signr, siginfo_t *info) 
	 * have updated *info via PTRACE_SETSIGINFO.

	 */

	if (signr != info->si_signo) {

		clear_siginfo(info);

		info->si_signo = signr;

		info->si_errno = 0;

		info->si_code = SI_USER;
@@ -2941,6 +2947,7 @@ SYSCALL_DEFINE2(kill, pid_t, pid, int, sig) 
{

	struct siginfo info;



	clear_siginfo(&info);

	info.si_signo = sig;

	info.si_errno = 0;

	info.si_code = SI_USER;