Re: [REPOST PATCH] crypto: caam - reject overlong RSA CRT parameters

[Herbert Xu]

On Thu, Oct 08, 2026 at 09:35:53AM +0000, Jérémy Jean wrote:
> caam_read_rsa_crt() right-aligns dP, dQ, and qInv in buffers sized
> from the corresponding prime. rsa_parse_priv_key() only bounds these
> integers against n, so a malformed key can provide, for example, a
> two-byte dP with a one-byte p. dstlen - nbytes then underflows and
> memcpy() writes outside the allocation during set_priv_key(). KASAN
> reports a slab-out-of-bounds write in caam_read_rsa_crt().
> 
> Reject empty or overlong CRT parameters after stripping leading zeros.
> qInv is consumed by CAAM as a p-sized value, so size it from p rather
> than q to match the DMA mapping in set_rsa_priv_f3_pdb(). Let the
> top-level key cleanup handle partial form-3 allocations and return the
> specific error to the caller.
> 
> Also test nbytes before dereferencing it while stripping zeros, so an
> all-zero integer does not read one byte beyond its input.
> 
> Fixes: 4a651b122adb ("crypto: caam - add support for RSA key form 3")
> Cc: stable@xxxxxxxxxxxxxxx
> Assisted-by: LLM
> Signed-off-by: Jérémy Jean <Jeremy.Jean@xxxxxxxxxxxxxxxxx>
> ---
>  drivers/crypto/caam/caampkc.c | 69 +++++++++++++++--------------------
>  1 file changed, 30 insertions(+), 39 deletions(-)

Sahil, could you please review this patch?

Thanks,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt