From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
This patch fixes a percpu_ref_put race for se_lun->lun_ref in
transport_lun_remove_cmd() where ->lun_ref could end up being
put more than once per command via different target completion
and fabric release contexts.
It adds a cmpxchg() for se_cmd->lun_ref_active to ensure that
percpu_ref_put() is only ever called once per se_cmd.
This bug was manifesting itself as a LUN shutdown regression
bug in >= v3.13 code, where percpu_ref_kill() would end up
hanging indefinately due to the incorrect percpu_ref count.
Reported-by: Tommy Apel <tommyapeldk@xxxxxxxxx>
Cc: Tommy Apel <tommyapeldk@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> #3.13+
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
drivers/target/target_core_transport.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 51a9736..c50fd9f 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -594,10 +594,11 @@ static void transport_lun_remove_cmd(struct se_cmd *cmd)
{
struct se_lun *lun = cmd->se_lun;
- if (!lun || !cmd->lun_ref_active)
+ if (!lun)
return;
- percpu_ref_put(&lun->lun_ref);
+ if (cmpxchg(&cmd->lun_ref_active, true, false))
+ percpu_ref_put(&lun->lun_ref);
}
void transport_cmd_finish_abort(struct se_cmd *cmd, int remove)
--
1.7.10.4
--
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