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Subject[PATCH] firmware: arm_scmi: Relax BASE protocol sanity checks on protocol list
Date
Even though malformed replies from firmware must be treated carefully to
avoid memory corruption Kernel side, some out-of-spec SCMI replies can
be tolerated to avoid breaking existing deployed system, as long as they
won't cause memory issues.

Reported-by: Nicolas Frattaroli <frattaroli.nicolas@gmail.com>
Cc: Etienne Carriere <etienne.carriere@linaro.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
drivers/firmware/arm_scmi/base.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/firmware/arm_scmi/base.c b/drivers/firmware/arm_scmi/base.c
index 20fba7370f4e..d0ac96da1ddf 100644
--- a/drivers/firmware/arm_scmi/base.c
+++ b/drivers/firmware/arm_scmi/base.c
@@ -221,11 +221,17 @@ scmi_base_implementation_list_get(const struct scmi_protocol_handle *ph,
calc_list_sz = (1 + (loop_num_ret - 1) / sizeof(u32)) *
sizeof(u32);
if (calc_list_sz != real_list_sz) {
- dev_err(dev,
- "Malformed reply - real_sz:%zd calc_sz:%u\n",
- real_list_sz, calc_list_sz);
- ret = -EPROTO;
- break;
+ dev_warn(dev,
+ "Malformed reply - real_sz:%zd calc_sz:%u (loop_num_ret:%d)\n",
+ real_list_sz, calc_list_sz, loop_num_ret);
+ /*
+ * Bail out if the expected list size is bigger than the
+ * total payload size of the received reply.
+ */
+ if (calc_list_sz > real_list_sz) {
+ ret = -EPROTO;
+ break;
+ }
}

for (loop = 0; loop < loop_num_ret; loop++)
--
2.36.1
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