[PATCH 4.19 128/313] tee: optee: avoid possible double list_del()

Greg Kroah-Hartman
2019-02-11T14:46:03Z

[ Upstream commit b2d102bd0146d9eb1fa630ca0cd19a15ef2f74c8 ]

This bug occurs when:

- a new request arrives, one thread(let's call it A) is pending in
optee_supp_req() with req->busy is initial value false.

- tee-supplicant is killed, then optee_supp_release() is called, this
function calls list_del(&req->link), and set supp->ctx to NULL. And
it also wake up process A.

- process A continues, it firstly checks supp->ctx which is NULL,
then checks req->busy which is false, at last run list_del(&req->link).
This triggers double list_del() and results kernel panic.

For solve this problem, we rename req->busy to req->in_queue, and
associate it with state of whether req is linked to supp->reqs. So we
can just only check req->in_queue to make decision calling list_del()
or not.

Signed-off-by: Zhizhou Zhang <zhizhouzhang@asrmicro.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tee/optee/supp.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/tee/optee/supp.c b/drivers/tee/optee/supp.c
index df35fc01fd3e..43626e15703a 100644
--- a/drivers/tee/optee/supp.c
+++ b/drivers/tee/optee/supp.c
@@ -19,7 +19,7 @@
struct optee_supp_req {
struct list_head link;

- bool busy;
+ bool in_queue;
u32 func;
u32 ret;
size_t num_params;
@@ -54,7 +54,6 @@ void optee_supp_release(struct optee_supp *supp)

/* Abort all request retrieved by supplicant */
idr_for_each_entry(&supp->idr, req, id) {
- req->busy = false;
idr_remove(&supp->idr, id);
req->ret = TEEC_ERROR_COMMUNICATION;
complete(&req->c);
@@ -63,6 +62,7 @@ void optee_supp_release(struct optee_supp *supp)
/* Abort all queued requests */
list_for_each_entry_safe(req, req_tmp, &supp->reqs, link) {
list_del(&req->link);
+ req->in_queue = false;
req->ret = TEEC_ERROR_COMMUNICATION;
complete(&req->c);
}
@@ -103,6 +103,7 @@ u32 optee_supp_thrd_req(struct tee_context *ctx, u32 func, size_t num_params,
/* Insert the request in the request list */
mutex_lock(&supp->mutex);
list_add_tail(&req->link, &supp->reqs);
+ req->in_queue = true;
mutex_unlock(&supp->mutex);

/* Tell an eventual waiter there's a new request */
@@ -130,9 +131,10 @@ u32 optee_supp_thrd_req(struct tee_context *ctx, u32 func, size_t num_params,
* will serve all requests in a timely manner and
* interrupting then wouldn't make sense.
*/
- interruptable = !req->busy;
- if (!req->busy)
+ if (req->in_queue) {
list_del(&req->link);
+ req->in_queue = false;
+ }
}
mutex_unlock(&supp->mutex);

@@ -176,7 +178,7 @@ static struct optee_supp_req *supp_pop_entry(struct optee_supp *supp,
return ERR_PTR(-ENOMEM);

list_del(&req->link);
- req->busy = true;
+ req->in_queue = false;

return req;
}
@@ -318,7 +320,6 @@ static struct optee_supp_req *supp_pop_req(struct optee_supp *supp,
if ((num_params - nm) != req->num_params)
return ERR_PTR(-EINVAL);

- req->busy = false;
idr_remove(&supp->idr, id);
supp->req_id = -1;
*num_meta = nm;
--
2.19.1