File xfs_repair-clear-pthread_t-when-pthread_create-fails.patch of Package xfsprogs.6453

From: Jeff Mahoney <jeffm@suse.com>
Subject: xfs_repair: clear pthread_t when pthread_create fails
Git-commit: 53dc81db1c86bc69c7e99961f5519e4d259a8f8d
Patch-mainline: v4.13.0
References: bsc#1019938

pf_queuing_worker and pf_create_prefetch_thread both try to handle
thread creation failure gracefully, but assume that pthread_create
doesn't modify the pthread_t when it fails.

>From the pthread_create man page:
On  success,  pthread_create() returns 0; on error, it returns an error
number, and the contents of *thread are undefined.

In fact, glibc's pthread_create writes the pthread_t value before
calling clone().  When we join the created threads in
cleanup_inode_prefetch and the cleanup stage of pf_queuing_worker, we
assume that if the pthread_t is nonzero that it's a valid thread handle
and end up crashing in pthread_join.

This patch zeros out the handle after pthread_create failure.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---
 repair/prefetch.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/repair/prefetch.c b/repair/prefetch.c
index ff506061..044fab2e 100644
--- a/repair/prefetch.c
+++ b/repair/prefetch.c
@@ -703,6 +703,7 @@ pf_queuing_worker(
 		if (err != 0) {
 			do_warn(_("failed to create prefetch thread: %s\n"),
 				strerror(err));
+			args->io_threads[i] = 0;
 			if (i == 0) {
 				pf_start_processing(args);
 				return NULL;
@@ -816,6 +817,7 @@ pf_create_prefetch_thread(
 	if (err != 0) {
 		do_warn(_("failed to create prefetch thread: %s\n"),
 			strerror(err));
+		args->queuing_thread = 0;
 		cleanup_inode_prefetch(args);
 	}