From 32ac8727bd4f427e2a2990af75915cbd4058bca4 Mon Sep 17 00:00:00 2001
From: gahr <gahr@ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f>
Date: Thu, 20 Jun 2013 16:50:05 +0000
Subject: [PATCH] MFC: r249406

- Do not bail out if stat(2) fails with ENOENT in the spool directory. This
  happens if another atrm process removes a job while we're scanning through
  the directory.
- While at it, optimize a bit the directory scanning, so that we quit
  looping as soon as all jobs specified in argv have been dealt with.

Approved by:	cognet


git-svn-id: svn://svn.freebsd.org/base/stable/8@252034 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
---
 usr.bin/at/at.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/usr.bin/at/at.c b/usr.bin/at/at.c
index 862948754..2fd5e75f0 100644
--- a/usr.bin/at/at.c
+++ b/usr.bin/at/at.c
@@ -533,6 +533,10 @@ process_jobs(int argc, char **argv, int what)
     /* Delete every argument (job - ID) given
      */
     int i;
+    int rc;
+    int nofJobs;
+    int nofDone;
+    int statErrno;
     struct stat buf;
     DIR *spool;
     struct dirent *dirent;
@@ -540,6 +544,9 @@ process_jobs(int argc, char **argv, int what)
     char queue;
     long jobno;
 
+    nofJobs = argc - optind;
+    nofDone = 0;
+
     PRIV_START
 
     if (chdir(ATJOB_DIR) != 0)
@@ -555,9 +562,20 @@ process_jobs(int argc, char **argv, int what)
     while((dirent = readdir(spool)) != NULL) {
 
 	PRIV_START
-	if (stat(dirent->d_name, &buf) != 0)
-	    perr("cannot stat in " ATJOB_DIR);
+	rc = stat(dirent->d_name, &buf);
+	statErrno = errno;
 	PRIV_END
+	/* There's a race condition between readdir above and stat here:
+	 * another atrm process could have removed the file from the spool
+	 * directory under our nose. If this happens, stat will set errno to
+	 * ENOENT, which we shouldn't treat as fatal.
+	 */
+	if (rc != 0) {
+	    if (statErrno == ENOENT)
+		continue;
+	    else
+		perr("cannot stat in " ATJOB_DIR);
+	}
 
 	if(sscanf(dirent->d_name, "%c%5lx%8lx", &queue, &jobno, &ctm)!=3)
 	    continue;
@@ -603,9 +621,15 @@ process_jobs(int argc, char **argv, int what)
 		    errx(EXIT_FAILURE, "internal error, process_jobs = %d",
 			what);
 	        }
+
+		/* All arguments have been processed
+		 */
+		if (++nofDone == nofJobs)
+		    goto end;
 	    }
 	}
     }
+end:
     closedir(spool);
 } /* delete_jobs */
 
-- 
2.45.0