From 185ec4397e61ad00dd68c841e15eaa8629eb9514 Mon Sep 17 00:00:00 2001 From: Coly Li Date: Sat, 11 Apr 2020 00:24:46 +0800 Subject: [RHEL7.9 PATCH 71/77] 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/, - 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//comm - if the file does not exit, it means the directory /proc/ does not exist, go to 4) - if the file exits, continue next step 3) Read process command name from /proc//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 Signed-off-by: Coly Li Signed-off-by: Jes Sorensen --- 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