commit 13a26601fb269c3e5da27de97288b9fcd63b61a2
author Jerome Forissier <jerome.forissier@linaro.org> Tue Mar 12 16:21:10 2019 +0100
committer Jérôme Forissier <jerome.forissier@linaro.org> Mon May 13 15:58:03 2019 +0200
tree 60f6343978c9172436684d2bdbb66ea8042d594d
parent cc6bc5f94210ea24b774c997fd482c936735db71

core: thread: use READ_ONCE() when accessing data in shared memory

In some places we read a value from shared memory, then based on the
value we take some actions. When multiple tests are done, we should make
sure that the value is not read multiple times because there is no
guarantee that Normal World has not changed the value in the mean time,
which could break the logic. Consider for instance:

	if (shared && shared->value)
		do_something();

If "shared" resides in shared memory, it might change between
"if (shared)" and "if (shared->value)". If it happens to be set to NULL
for example, the code will crash.
To ensure consistency, a temporary variable has to be used to hold the
value, and the READ_ONCE() macro is required to prevent the compiler
from emitting multiple loads of the memory location.

Reported-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>