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

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Commit 2e4955167e ("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>
This commit is contained in:
Krzysztof Kozlowski
2024-12-09 15:27:55 +01:00
committed by Bjorn Andersson
parent 0a744cceeb
commit b628510397
1 changed files with 4 additions and 1 deletions
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5
drivers/firmware/qcom/qcom_scm.c
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@@ -217,7 +217,10 @@ static DEFINE_SPINLOCK(scm_query_lock);
struct qcom_tzmem_pool *qcom_scm_get_tzmem_pool(void)
{
return __scm ? __scm->mempool : NULL;
if (!qcom_scm_is_available())
return NULL;
return __scm->mempool;
}
static enum qcom_scm_convention __get_convention(void)