linux-kernel - [PATCH 1/1] Fix kill(-1,s) returning 0 on 0 kills

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Date:   Tue, 22 Nov 2022 17:12:41 +0100
From:   Petr Skocik <pskocik@...il.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Oleg Nesterov <oleg@...hat.com>, Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Marco Elver <elver@...gle.com>, linux-kernel@...r.kernel.org,
        Petr Skocik <pskocik@...il.com>
Subject: [PATCH 1/1] Fix kill(-1,s) returning 0 on 0 kills

Make kill(-1,s) return -ESRCH when it has nothing to kill.
It's the sensible thing to do, it's what FreeBSD does, and
it also seems to be the unrealized intention of the original code.

Signed-off-by: Petr Skocik <pskocik@...il.com>
---
 kernel/signal.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index d140672185a4..02e7c85c7152 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1600,20 +1600,18 @@ static int kill_something_info(int sig, struct kernel_siginfo *info, pid_t pid)
 		ret = __kill_pgrp_info(sig, info,
 				pid ? find_vpid(-pid) : task_pgrp(current));
 	} else {
-		int retval = 0, count = 0;
 		struct task_struct * p;
 
+		ret = -ESRCH;
 		for_each_process(p) {
 			if (task_pid_vnr(p) > 1 &&
 					!same_thread_group(p, current)) {
 				int err = group_send_sig_info(sig, info, p,
 							      PIDTYPE_MAX);
-				++count;
 				if (err != -EPERM)
-					retval = err;
+					ret = err; /*either all 0 or all -EINVAL*/
 			}
 		}
-		ret = count ? retval : -ESRCH;
 	}
 	read_unlock(&tasklist_lock);
 
-- 
2.25.1