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")

kernel.org https://git.kernel.org/stable/c/4c65507121ea8e0b47fae6d2049c8688390d46b6 [No types assigned]

kernel.org https://git.kernel.org/stable/c/d0d04efa2e367921654b5106cc5c05e3757c2b42 [No types assigned]

kernel.org https://git.kernel.org/stable/c/de1bf25b6d771abdb52d43546cf57ad775fb68a1 [No types assigned]