[PATCH AUTOSEL 4.19 383/671] signal/bpfilter: Fix bpfilter_kernl to use send_sig not force_sig

Sasha Levin
2020-01-16T18:54:19Z

From: "Eric W. Biederman" <ebiederm@xmission.com>

[ Upstream commit 1dfd1711de2952fd1bfeea7152bd1687a4eea771 ]

The locking in force_sig_info is not prepared to deal with
a task that exits or execs (as sighand may change). As force_sig
is only built to handle synchronous exceptions.

Further the function force_sig_info changes the signal state if the
signal is ignored, or blocked or if SIGNAL_UNKILLABLE will prevent the
delivery of the signal. The signal SIGKILL can not be ignored and can
not be blocked and SIGNAL_UNKILLABLE won't prevent it from being
delivered.

So using force_sig rather than send_sig for SIGKILL is pointless.

Because it won't impact the sending of the signal and and because
using force_sig is wrong, replace force_sig with send_sig.

Cc: Alexei Starovoitov <ast@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Fixes: d2ba09c17a06 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/bpfilter/bpfilter_kern.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
index 94e88f510c5b..450b257afa84 100644
--- a/net/bpfilter/bpfilter_kern.c
+++ b/net/bpfilter/bpfilter_kern.c
@@ -25,7 +25,7 @@ static void shutdown_umh(struct umh_info *info)
return;
tsk = get_pid_task(find_vpid(info->pid), PIDTYPE_PID);
if (tsk) {
- force_sig(SIGKILL, tsk);
+ send_sig(SIGKILL, tsk, 1);
put_task_struct(tsk);
}
fput(info->pipe_to_umh);
--
2.20.1