When two iscsi ips log in and out alternately and the following scripts run
at the same time,
#!/bin/bash
interval=5
while true
do
iscsiadm -m node -p 9.41.147.171 &> /dev/null
iscsiadm -m node -p 9.41.148.172 &> /dev/null
iscsiadm -m session &> /dev/null
rescan-scsi-bus.sh &> /dev/null
multipath -v2 &> /dev/null
multipath -ll &> /dev/null
sleep $interval
done
multipathd will have a segfault after about 30 mins.
The reason is that mpp->hwe is accessed after hwe is already freed. In
extract_hwe_from_path func, mpp->hwe is set to pp->hwe, so they points to the
same hwe. For some reasons, pp->mpp will be set to NULL in orphan_path func.
Then, pp and hwe will be freed with (pp->mpp == NULL) in free_path func
called by ev_remove_path func. However, mpp->hwe is not set to NULL while hwe
is already freed. So, when iscsi device logs in and new path is added to mpp,
mpp->hwe will be accessed in select_pgfailback func. Finally, use-after-free
problem occurs.
The procedure details given as follows,
1.wait_dmevents thread
wait_dmevents
->dmevent_loop
->update_multipath
->__setup_multipath
->update_multipath_strings
-> sync_paths
->orphan_path
2.uevqloop thread (iscsi log out, remove path)
uevqloop
->uevent_dispatch
->service_uevq
->uev_remove_path
->ev_remove_path //pp->mpp is NULL
->free_path(pp)
//pp->hew are freed but mpp->hwe is not set to NULL
3.ev_remove_path (iscsi log in, add path)
uevqloop
->uevent_dispatch
->service_uevq
->ev_add_path
->select_pgfailback //mpp->hwe is accessed
Here, we will set mpp->hwe to NULL before setting pp->map to NULL in orphan_path
func.
Signed-off-by: Tianxiong Lu <lutianxiong@xxxxxxxxxx>
Signed-off-by: lixiaokeng <lixiaokeng@xxxxxxxxxx>
Signed-off-by: Zhiqiang Liu <liuzhiqiang26@xxxxxxxxxx>
---
libmultipath/structs_vec.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/libmultipath/structs_vec.c b/libmultipath/structs_vec.c
index 3dbbaa0..9bbe5d1 100644
--- a/libmultipath/structs_vec.c
+++ b/libmultipath/structs_vec.c
@@ -93,6 +93,8 @@ int adopt_paths(vector pathvec, struct multipath *mpp)
void orphan_path(struct path *pp, const char *reason)
{
condlog(3, "%s: orphan path, %s", pp->dev, reason);
+ if (pp->mpp && pp->mpp->hwe == pp->hwe)
+ pp->mpp->hwe = NULL;
pp->mpp = NULL;
pp->dmstate = PSTATE_UNDEF;
pp->uid_attribute = NULL;
--
2.26.1
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
