From: Wang Shilong <wshilong@ddn.com>
Date: Mon, 29 Apr 2019 12:46:47 +0000 (+0800)
Subject: LU-12225 obdclass: fix race access vs removal of jobid_hash
X-Git-Tag: 2.12.54~83
X-Git-Url: https://git.whamcloud.com/?a=commitdiff_plain;h=b664182e0361731fa409ac6a0a0f19637a7e5288;p=fs%2Flustre-release.git

LU-12225 obdclass: fix race access vs removal of jobid_hash

We added @pidmap into hash and reference count will be 1.
However, another thread might reclaim this newely added
@pidmap from hash list, we try to access this @pidmap
will become a user-after-free operation.

Fix this problem by init reference count as 1 before
adding hash list, which gurantee memory could be not
freed during our access.

Check other places where memory reclaim used did similar
idea like this.

Change-Id: Idd5f429b97e064e29b6883243f8a012c2b4b4ae7
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-on: https://review.whamcloud.com/34763
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
---

diff --git a/lustre/obdclass/jobid.c b/lustre/obdclass/jobid.c
index 633388b..07a6c57 100644
--- a/lustre/obdclass/jobid.c
+++ b/lustre/obdclass/jobid.c
@@ -213,6 +213,12 @@ static int jobid_get_from_cache(char *jobid, size_t joblen)
 		pidmap->jp_jobid[0] = '\0';
 		spin_lock_init(&pidmap->jp_lock);
 		INIT_HLIST_NODE(&pidmap->jp_hash);
+		/*
+		 * @pidmap might be reclaimed just after it is added into
+		 * hash list, init @jp_refcount as 1 to make sure memory
+		 * could be not freed during access.
+		 */
+		atomic_set(&pidmap->jp_refcount, 1);
 
 		/*
 		 * Add the newly created map to the hash, on key collision we
@@ -226,8 +232,6 @@ static int jobid_get_from_cache(char *jobid, size_t joblen)
 			       pid);
 			OBD_FREE_PTR(pidmap);
 			pidmap = pidmap2;
-		} else {
-			cfs_hash_get(jobid_hash, &pidmap->jp_hash);
 		}
 	}