From 185ec4397e61ad00dd68c841e15eaa8629eb9514 Mon Sep 17 00:00:00 2001

From: Coly Li <colyli@suse.de>

Date: Sat, 11 Apr 2020 00:24:46 +0800

Subject: [RHEL7.9 PATCH 68/71] Monitor: improve check_one_sharer() for

 checking duplicated process

When running mdadm monitor with scan mode, only one autorebuild process

is allowed. check_one_sharer() checks duplicated process by following

steps,

1) Read autorebuild.pid file,

   - if file does not exist, no duplicated process, go to 3).

   - if file exists, continue to next step.

2) Read pid number from autorebuild.pid file, then check procfs pid

   directory /proc/<PID>,

   - if the directory does not exist, no duplicated process, go to 3)

   - if the directory exists, print error message for duplicated process

     and exit this mdadm.

3) Write current pid into autorebuild.pid file, continue to monitor in

   scan mode.

The problem for the above step 2) is, if after system reboots and

another different process happens to have exact same pid number which

autorebuild.pid file records, check_one_sharer() will treat it as a

duplicated mdadm process and returns error with message "Only one

autorebuild process allowed in scan mode, aborting".

This patch tries to fix the above same-pid-but-different-process issue

by one more step to check the process command name,

1) Read autorebuild.pid file

   - if file does not exist, no duplicated process, go to 4).

   - if file exists, continue to next step.

2) Read pid number from autorebuild.pid file, then check procfs file

   comm with the specific pid directory /proc/<PID>/comm

   - if the file does not exit, it means the directory /proc/<PID> does

     not exist, go to 4)

   - if the file exits, continue next step

3) Read process command name from /proc/<PIC>/comm, compare the command

   name with "mdadm" process name,

   - if not equal, no duplicated process, goto 4)

   - if strings are equal, print error message for duplicated process

     and exit this mdadm.

4) Write current pid into autorebuild.pid file, continue to monitor in

   scan mode.

Now check_one_sharer() returns error for duplicated process only when

the recorded pid from autorebuild.pid exists, and the process has exact

same command name as "mdadm".

Reported-by: Shinkichi Yamazaki <shinkichi.yamazaki@suse.com>

Signed-off-by: Coly Li <colyli@suse.de>

Signed-off-by: Jes Sorensen <jsorensen@fb.com>

---

 Monitor.c | 32 ++++++++++++++++++++------------

 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/Monitor.c b/Monitor.c

index b527165..2d6b3b9 100644

--- a/Monitor.c

+++ b/Monitor.c

@@ -301,26 +301,34 @@ static int make_daemon(char *pidfile)

 static int check_one_sharer(int scan)

 {

-	int pid, rv;

+	int pid;

+	FILE *comm_fp;

 	FILE *fp;

-	char dir[20];

+	char comm_path[100];

 	char path[100];

-	struct stat buf;

+	char comm[20];

+

 	sprintf(path, "%s/autorebuild.pid", MDMON_DIR);

 	fp = fopen(path, "r");

 	if (fp) {

 		if (fscanf(fp, "%d", &pid) != 1)

 			pid = -1;

-		sprintf(dir, "/proc/%d", pid);

-		rv = stat(dir, &buf;;

-		if (rv != -1) {

-			if (scan) {

-				pr_err("Only one autorebuild process allowed in scan mode, aborting\n");

-				fclose(fp);

-				return 1;

-			} else {

-				pr_err("Warning: One autorebuild process already running.\n");

+		snprintf(comm_path, sizeof(comm_path),

+			 "/proc/%d/comm", pid);

+		comm_fp = fopen(comm_path, "r");

+		if (comm_fp) {

+			if (fscanf(comm_fp, "%s", comm) &&

+			    strncmp(basename(comm), Name, strlen(Name)) == 0) {

+				if (scan) {

+					pr_err("Only one autorebuild process allowed in scan mode, aborting\n");

+					fclose(comm_fp);

+					fclose(fp);

+					return 1;

+				} else {

+					pr_err("Warning: One autorebuild process already running.\n");

+				}

 			}

+			fclose(comm_fp);

 		}

 		fclose(fp);

 	}

-- 

2.7.5