CVE-2024-58084

In the Linux kernel, the following vulnerability has been resolved:

firmware: qcom: scm: Fix missing read barrier in qcomscmgettzmempool()

Commit 2e4955167ec5 ("firmware: qcom: scm: Fix _scm and waitq completion variable initialization") introduced a write barrier in probe function to store global 'scm' variable. We all known barriers are paired (see memory-barriers.txt: "Note that write barriers should normally be paired with read or address-dependency barriers"), therefore accessing it from concurrent contexts requires read barrier. Previous commit added such barrier in qcomscmisavailable(), so let's use that directly.

Lack of this read barrier can result in fetching stale '__scm' variable value, NULL, and dereferencing it.

Note that barrier in qcomscmis_available() satisfies here the control dependency.