6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mike Tipton quic_mdtipton@quicinc.com
[ Upstream commit de1bf25b6d771abdb52d43546cf57ad775fb68a1 ]
The icc_lock mutex was split into separate icc_lock and icc_bw_lock mutexes in [1] to avoid lockdep splats. However, this didn't adequately protect access to icc_node::req_list.
The icc_set_bw() function will eventually iterate over req_list while only holding icc_bw_lock, but req_list can be modified while only holding icc_lock. This causes races between icc_set_bw(), of_icc_get(), and icc_put().
Example A:
CPU0 CPU1 ---- ---- icc_set_bw(path_a) mutex_lock(&icc_bw_lock); icc_put(path_b) mutex_lock(&icc_lock); aggregate_requests() hlist_for_each_entry(r, ... hlist_del(... <r = invalid pointer>
Example B:
CPU0 CPU1 ---- ---- icc_set_bw(path_a) mutex_lock(&icc_bw_lock); path_b = of_icc_get() of_icc_get_by_index() mutex_lock(&icc_lock); path_find() path_init() aggregate_requests() hlist_for_each_entry(r, ... hlist_add_head(... <r = invalid pointer>
Fix this by ensuring icc_bw_lock is always held before manipulating icc_node::req_list. The additional places icc_bw_lock is held don't perform any memory allocations, so we should still be safe from the original lockdep splats that motivated the separate locks.
[1] commit af42269c3523 ("interconnect: Fix locking for runpm vs reclaim")
Signed-off-by: Mike Tipton quic_mdtipton@quicinc.com Fixes: af42269c3523 ("interconnect: Fix locking for runpm vs reclaim") Reviewed-by: Rob Clark robdclark@chromium.org Link: https://lore.kernel.org/r/20240305225652.22872-1-quic_mdtipton@quicinc.com Signed-off-by: Georgi Djakov djakov@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/interconnect/core.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c index 50bac2d79d9b5..68edb07d4443e 100644 --- a/drivers/interconnect/core.c +++ b/drivers/interconnect/core.c @@ -176,6 +176,8 @@ static struct icc_path *path_init(struct device *dev, struct icc_node *dst,
path->num_nodes = num_nodes;
+ mutex_lock(&icc_bw_lock); + for (i = num_nodes - 1; i >= 0; i--) { node->provider->users++; hlist_add_head(&path->reqs[i].req_node, &node->req_list); @@ -186,6 +188,8 @@ static struct icc_path *path_init(struct device *dev, struct icc_node *dst, node = node->reverse; }
+ mutex_unlock(&icc_bw_lock); + return path; }
@@ -792,12 +796,16 @@ void icc_put(struct icc_path *path) pr_err("%s: error (%d)\n", __func__, ret);
mutex_lock(&icc_lock); + mutex_lock(&icc_bw_lock); + for (i = 0; i < path->num_nodes; i++) { node = path->reqs[i].node; hlist_del(&path->reqs[i].req_node); if (!WARN_ON(!node->provider->users)) node->provider->users--; } + + mutex_unlock(&icc_bw_lock); mutex_unlock(&icc_lock);
kfree_const(path->name);