From: Roy Marples <roy@marples.name>
Date: Fri, 2 Sep 2022 11:54:25 +0000 (+0100)
Subject: privsep: Don't find processes we just asked to stop
X-Git-Tag: v10.0.0~31
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ce13b79d78df81de388b2448d4edce4f3e16c66a;p=thirdparty%2Fdhcpcd.git

privsep: Don't find processes we just asked to stop

We could rebind a lease, get a NAK and enter DISCOVER.
We need to restart the BPF in the middle as the BPF filter could
change.

As such, add a started flag to each privsep process and when
searching for a process by id only find started ones.
If we ask them to stop then the started flag is removed.

Fixes errors about writing to stopping processes an unknown
processes exiting.
---

diff --git a/src/privsep.c b/src/privsep.c
index f08b4028..5a437ae3 100644
--- a/src/privsep.c
+++ b/src/privsep.c
@@ -408,6 +408,7 @@ ps_startprocess(struct ps_process *psp,
 			return -1;
 		}
 #endif
+		psp->psp_started = true;
 		return pid;
 	}
 
@@ -481,6 +482,7 @@ ps_startprocess(struct ps_process *psp,
 	if (flags & PSF_DROPPRIVS)
 		ps_dropprivs(ctx);
 
+	psp->psp_started = true;
 	return 0;
 
 errexit:
@@ -509,6 +511,8 @@ ps_stopprocess(struct ps_process *psp)
 	if (psp == NULL)
 		return 0;
 
+	psp->psp_started = false;
+
 #ifdef PRIVSEP_DEBUG
 	logdebugx("%s: me=%d pid=%d fd=%d %s", __func__,
 	    getpid(), psp->psp_pid, psp->psp_fd, psp->psp_name);
@@ -1164,6 +1168,8 @@ ps_findprocess(struct dhcpcd_ctx *ctx, struct ps_id *psid)
 	struct ps_process *psp;
 
 	TAILQ_FOREACH(psp, &ctx->ps_processes, next) {
+		if (!(psp->psp_started))
+			continue;
 		if (memcmp(&psp->psp_id, psid, sizeof(psp->psp_id)) == 0)
 			return psp;
 	}
diff --git a/src/privsep.h b/src/privsep.h
index 856848e0..2f0304a7 100644
--- a/src/privsep.h
+++ b/src/privsep.h
@@ -169,6 +169,7 @@ struct ps_msg {
 };
 
 struct bpf;
+
 struct ps_process {
 	TAILQ_ENTRY(ps_process) next;
 	struct dhcpcd_ctx *psp_ctx;
@@ -181,6 +182,7 @@ struct ps_process {
 	char psp_name[PSP_NAMESIZE];
 	uint16_t psp_proto;
 	const char *psp_protostr;
+	bool psp_started;
 
 #ifdef INET
 	int (*psp_filter)(const struct bpf *, const struct in_addr *);