pstore/ram: Add check for kstrdup

pstore/ram: Add check for kstrdup

[ Upstream commit d97038d5ec2062733c1e016caf9baaf68cf64ea1 ]

Add check for the return value of kstrdup() and return the error
if it fails in order to avoid NULL pointer dereference.

Fixes: e163fdb3f7f8 ("pstore/ram: Regularize prz label allocation lifetime")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230614093733.36048-1-jiasheng@iscas.ac.cn
Signed-off-by: Sasha Levin <sashal@kernel.org>