interconnect: Don't access req_list while it's being manipulated

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: interconnect: Don't access req_list while it's being manipulated 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")

References

• https://git.kernel.org/stable/c/fe549d8e976300d0dd75bd904eb216bed8b145e0
• https://git.kernel.org/stable/c/19ec82b3cad1abef2a929262b8c1528f4e0c192d
• https://git.kernel.org/stable/c/d0d04efa2e367921654b5106cc5c05e3757c2b42
• https://git.kernel.org/stable/c/4c65507121ea8e0b47fae6d2049c8688390d46b6
• https://git.kernel.org/stable/c/de1bf25b6d771abdb52d43546cf57ad775fb68a1