Re: [PATCH v5 2/2] KEYS: asymmetric: Copy sig and digest in public_key_verify_signature()

[Eric Biggers]

On Tue, Dec 27, 2022 at 03:27:40PM +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> 
> Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear
> mapping") checks that both the signature and the digest reside in the
> linear mapping area.
> 
> However, more recently commit ba14a194a434c ("fork: Add generic vmalloced
> stack support") made it possible to move the stack in the vmalloc area,
> which is not contiguous, and thus not suitable for sg_set_buf() which needs
> adjacent pages.
> 
> Always make a copy of the signature and digest in the same buffer used to
> store the key and its parameters, and pass them to sg_init_one(). Prefer it
> to conditionally doing the copy if necessary, to keep the code simple. The
> buffer allocated with kmalloc() is in the linear mapping area.
> 
> Cc: stable@xxxxxxxxxxxxxxx # 4.9.x
> Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> Link: https://lore.kernel.org/linux-integrity/Y4pIpxbjBdajymBJ@sol.localdomain/
> Suggested-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> ---
>  crypto/asymmetric_keys/public_key.c | 38 ++++++++++++++++-------------
>  1 file changed, 21 insertions(+), 17 deletions(-)

Reviewed-by: Eric Biggers <ebiggers@xxxxxxxxxx>

- Eric