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s390/archrandom: add parameter check for s390_arch_random_generate

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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>
This commit is contained in:
Harald Freudenberger 2021-04-20 08:23:12 +02:00 committed by Heiko Carstens
parent 70fac8088c
commit 2809606768
1 changed files with 4 additions and 0 deletions
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4
arch/s390/crypto/arch_random.c
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@ -54,6 +54,10 @@ 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;