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commitb628510397upstream. Commit2e4955167e("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 qcom_scm_is_available(), 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 qcom_scm_is_available() satisfies here the control dependency. Fixes:ca61d6836e("firmware: qcom: scm: fix a NULL-pointer dereference") Fixes:449d0d84bc("firmware: qcom: scm: smc: switch to using the SCM allocator") Cc: stable@vger.kernel.org Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Link: https://lore.kernel.org/r/20241209-qcom-scm-missing-barriers-and-all-sort-of-srap-v2-2-9061013c8d92@linaro.org Signed-off-by: Bjorn Andersson <andersson@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>