From: Harald Freudenberger <freude@linux.ibm.com> [ Upstream commit 28096067686c5a5cbd4c35b079749bd805df5010 ] A review of the code showed, that this function which is exposed within the whole kernel should do a parameter check for the amount of bytes requested. If this requested bytes is too high an unsigned int overflow could happen causing this function to try to memcpy a really big memory chunk. This is not a security issue as there are only two invocations of this function from arch/s390/include/asm/archrandom.h and both are not exposed to userland. Reported-by: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Harald Freudenberger <freude@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- arch/s390/crypto/arch_random.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/s390/crypto/arch_random.c b/arch/s390/crypto/arch_random.c index dd95cdbd22ce8..4cbb4b6d85a83 100644 --- a/arch/s390/crypto/arch_random.c +++ b/arch/s390/crypto/arch_random.c @@ -53,6 +53,10 @@ static DECLARE_DELAYED_WORK(arch_rng_work, arch_rng_refill_buffer); bool s390_arch_random_generate(u8 *buf, unsigned int nbytes) { + /* max hunk is ARCH_RNG_BUF_SIZE */ + if (nbytes > ARCH_RNG_BUF_SIZE) + return false; + /* lock rng buffer */ if (!spin_trylock(&arch_rng_lock)) return false; -- 2.25.1