From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
commit b628510397b5cafa1f5d3e848a28affd1c635302 upstream.
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 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: ca61d6836e6f ("firmware: qcom: scm: fix a NULL-pointer dereference")
Fixes: 449d0d84bcd8 ("firmware: qcom: scm: smc: switch to using the SCM allocator")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241209-qcom-scm-missing-barriers-and-all-sort-of-srap-v2-2-9061013c8d92@xxxxxxxxxx
Signed-off-by: Bjorn Andersson <andersson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/firmware/qcom/qcom_scm.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
index cde60566c793..4a1c05a7bf20 100644
--- a/drivers/firmware/qcom/qcom_scm.c
+++ b/drivers/firmware/qcom/qcom_scm.c
@@ -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)
--
2.48.1
Patches currently in stable-queue which might be from krzysztof.kozlowski@xxxxxxxxxx are
queue-6.12/firmware-qcom-scm-fix-missing-read-barrier-in-qcom_scm_get_tzmem_pool.patch
queue-6.12/firmware-qcom-scm-fix-missing-read-barrier-in-qcom_scm_is_available.patch
