2022-04-27 11:12:25

by Eric W. Biederman

Subject: [PATCH 1/9] signal: Rename send_signal send_signal_locked

Rename send_signal send_signal_locked and make to make
it usable outside of signal.c.

Signed-off-by: "Eric W. Biederman" <[email protected]>
---
include/linux/signal.h | 2 ++
kernel/signal.c | 24 ++++++++++++------------
2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/include/linux/signal.h b/include/linux/signal.h
index a6db6f2ae113..55605bdf5ce9 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -283,6 +283,8 @@ extern int do_send_sig_info(int sig, struct kernel_siginfo *info,
extern int group_send_sig_info(int sig, struct kernel_siginfo *info,
struct task_struct *p, enum pid_type type);
extern int __group_send_sig_info(int, struct kernel_siginfo *, struct task_struct *);
+extern int send_signal_locked(int sig, struct kernel_siginfo *info,
+ struct task_struct *p, enum pid_type type);
extern int sigprocmask(int, sigset_t *, sigset_t *);
extern void set_current_blocked(sigset_t *);
extern void __set_current_blocked(const sigset_t *);
diff --git a/kernel/signal.c b/kernel/signal.c
index 30cd1ca43bcd..b0403197b0ad 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1071,8 +1071,8 @@ static inline bool legacy_queue(struct sigpending *signals, int sig)
return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
}

-static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t,
- enum pid_type type, bool force)
+static int __send_signal_locked(int sig, struct kernel_siginfo *info,
+ struct task_struct *t, enum pid_type type, bool force)
{
struct sigpending *pending;
struct sigqueue *q;
@@ -1212,8 +1212,8 @@ static inline bool has_si_pid_and_uid(struct kernel_siginfo *info)
return ret;
}

-static int send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t,
- enum pid_type type)
+int send_signal_locked(int sig, struct kernel_siginfo *info,
+ struct task_struct *t, enum pid_type type)
{
/* Should SIGKILL or SIGSTOP be received by a pid namespace init? */
bool force = false;
@@ -1245,7 +1245,7 @@ static int send_signal(int sig, struct kernel_siginfo *info, struct task_struct
force = true;
}
}
- return __send_signal(sig, info, t, type, force);
+ return __send_signal_locked(sig, info, t, type, force);
}

static void print_fatal_signal(int signr)
@@ -1284,7 +1284,7 @@ __setup("print-fatal-signals=", setup_print_fatal_signals);
int
__group_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p)
{
- return send_signal(sig, info, p, PIDTYPE_TGID);
+ return send_signal_locked(sig, info, p, PIDTYPE_TGID);
}

int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p,
@@ -1294,7 +1294,7 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p
int ret = -ESRCH;

if (lock_task_sighand(p, &flags)) {
- ret = send_signal(sig, info, p, type);
+ ret = send_signal_locked(sig, info, p, type);
unlock_task_sighand(p, &flags);
}

@@ -1347,7 +1347,7 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t,
if (action->sa.sa_handler == SIG_DFL &&
(!t->ptrace || (handler == HANDLER_EXIT)))
t->signal->flags &= ~SIGNAL_UNKILLABLE;
- ret = send_signal(sig, info, t, PIDTYPE_PID);
+ ret = send_signal_locked(sig, info, t, PIDTYPE_PID);
spin_unlock_irqrestore(&t->sighand->siglock, flags);

return ret;
@@ -1567,7 +1567,7 @@ int kill_pid_usb_asyncio(int sig, int errno, sigval_t addr,

if (sig) {
if (lock_task_sighand(p, &flags)) {
- ret = __send_signal(sig, &info, p, PIDTYPE_TGID, false);
+ ret = __send_signal_locked(sig, &info, p, PIDTYPE_TGID, false);
unlock_task_sighand(p, &flags);
} else
ret = -ESRCH;
@@ -2103,7 +2103,7 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
* parent's namespaces.
*/
if (valid_signal(sig) && sig)
- __send_signal(sig, &info, tsk->parent, PIDTYPE_TGID, false);
+ __send_signal_locked(sig, &info, tsk->parent, PIDTYPE_TGID, false);
__wake_up_parent(tsk, tsk->parent);
spin_unlock_irqrestore(&psig->siglock, flags);

@@ -2601,7 +2601,7 @@ static int ptrace_signal(int signr, kernel_siginfo_t *info, enum pid_type type)
/* If the (new) signal is now blocked, requeue it. */
if (sigismember(&current->blocked, signr) ||
fatal_signal_pending(current)) {
- send_signal(signr, info, current, type);
+ send_signal_locked(signr, info, current, type);
signr = 0;
}

@@ -4793,7 +4793,7 @@ void kdb_send_sig(struct task_struct *t, int sig)
"the deadlock.\n");
return;
}
- ret = send_signal(sig, SEND_SIG_PRIV, t, PIDTYPE_PID);
+ ret = send_signal_locked(sig, SEND_SIG_PRIV, t, PIDTYPE_PID);
spin_unlock(&t->sighand->siglock);
if (ret)
kdb_printf("Fail to deliver Signal %d to process %d.\n",
--
2.35.3

2022-04-28 14:23:42

by Peter Zijlstra

Subject: Re: [PATCH 1/9] signal: Rename send_signal send_signal_locked

On Tue, Apr 26, 2022 at 05:52:03PM -0500, Eric W. Biederman wrote:
> Rename send_signal send_signal_locked and make to make
> it usable outside of signal.c.
>
> Signed-off-by: "Eric W. Biederman" <[email protected]>
> ---
> include/linux/signal.h | 2 ++
> kernel/signal.c | 24 ++++++++++++------------
> 2 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/signal.h b/include/linux/signal.h
> index a6db6f2ae113..55605bdf5ce9 100644
> --- a/include/linux/signal.h
> +++ b/include/linux/signal.h
> @@ -283,6 +283,8 @@ extern int do_send_sig_info(int sig, struct kernel_siginfo *info,
> extern int group_send_sig_info(int sig, struct kernel_siginfo *info,
> struct task_struct *p, enum pid_type type);
> extern int __group_send_sig_info(int, struct kernel_siginfo *, struct task_struct *);
> +extern int send_signal_locked(int sig, struct kernel_siginfo *info,
> + struct task_struct *p, enum pid_type type);
> extern int sigprocmask(int, sigset_t *, sigset_t *);
> extern void set_current_blocked(sigset_t *);
> extern void __set_current_blocked(const sigset_t *);
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 30cd1ca43bcd..b0403197b0ad 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1071,8 +1071,8 @@ static inline bool legacy_queue(struct sigpending *signals, int sig)
> return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
> }
>
> -static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t,
> - enum pid_type type, bool force)
> +static int __send_signal_locked(int sig, struct kernel_siginfo *info,
> + struct task_struct *t, enum pid_type type, bool force)
> {
> struct sigpending *pending;
> struct sigqueue *q;

While there, could you please replace that assert_spin_locked() with
lockdep_assert_held(&t->sighand->siglock) ?

The distinction being that assert_spin_locked() checks if the lock is
held *by*anyone* whereas lockdep_assert_held() asserts the current
context holds the lock. Also, the check goes away if you build without
lockdep.