Re: Re: PING: [PATCH] crypto: public_key: fix overflow during implicit conversion

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, 2021-08-19 at 10:03 +0800, zhenwei pi wrote:
> On 8/18/21 8:33 PM, Jarkko Sakkinen wrote:
> > On Wed, 2021-08-18 at 16:33 +0800, zhenwei pi wrote:
> > > PING
> > 
> > Please, do not top-post.
> > 
> > You are lacking Herbert Xu:
> > 
> > $ scripts/get_maintainer.pl crypto/asymmetric_keys/public_key.c
> > David Howells <dhowells@redhat.com> (maintainer:ASYMMETRIC KEYS)
> > Herbert Xu <herbert@gondor.apana.org.au> (maintainer:CRYPTO API)
> > "David S. Miller" <davem@davemloft.net> (maintainer:CRYPTO API)
> > keyrings@vger.kernel.org (open list:ASYMMETRIC KEYS)
> > linux-crypto@vger.kernel.org (open list:CRYPTO API)
> > linux-kernel@vger.kernel.org (open list)
> > 
> > > On 8/10/21 2:39 PM, zhenwei pi wrote:
> > > > Hit kernel warning like this, it can be reproduced by verifying
> > > > 256
> > > > bytes datafile by keyctl command.
> > > > 
> > > >    WARNING: CPU: 5 PID: 344556 at crypto/rsa-pkcs1pad.c:540
> > > > pkcs1pad_verify+0x160/0x190
> > > >    ...
> > > >    Call Trace:
> > > >     public_key_verify_signature+0x282/0x380
> > > >     ? software_key_query+0x12d/0x180
> > > >     ? keyctl_pkey_params_get+0xd6/0x130
> > > >     asymmetric_key_verify_signature+0x66/0x80
> > > >     keyctl_pkey_verify+0xa5/0x100
> > > >     do_syscall_64+0x35/0xb0
> > > >     entry_SYSCALL_64_after_hwframe+0x44/0xae
> > > > 
> > > > '.digest_size(u8) = params->in_len(u32)' leads overflow of an
> > > > u8
> > 
> > Where is this statement?
> > 
> 
> In function "static int asymmetric_key_verify_signature(struct 
> kernel_pkey_params *params, const void *in, const void *in2)"
> 
> > > > value,
> > > > so use u32 instead of u8 of digest. And reorder struct
> > > > public_key_signature, it could save 8 bytes on a 64 bit
> > > > machine.
> >                                                       ~~~~~
> >                                                       64-bit
> >                                                       
> > What do you mean by "could"? Does it, or does it
> > not?
> >                                         				
> > 	
> > 
> After reordering struct public_key_signature, sizeof(struct 
> public_key_signature) gets smaller than the original version.

OK, then just state is as "it saves" instead of "it could save".

Not a requirement but have you been able to trigger this for a
kernel that does not have this fix?

/Jarkko