[PATCH v2] crypto: krb5 - filter out async aead implementations at alloc

[Herbert Xu]

On Sun, May 10, 2026 at 07:24:55PM -0400, Michael Bommarito wrote:
> krb5_aead_encrypt(), krb5_aead_decrypt() in rfc3961_simplified.c and
> rfc8009_encrypt(), rfc8009_decrypt() in rfc8009_aes2.c set a NULL
> completion callback and treat any negative return from
> crypto_aead_{encrypt,decrypt}() as terminal, falling through to
> kfree_sensitive(buffer).  When the encrypt_name resolves to an
> async AEAD instance the request returns -EINPROGRESS, the buffer
> is freed while the backend's worker still holds a pointer, and the
> worker dereferences the freed slab on completion.
> 
> KASAN report under UML+SLUB with a synthetic async aead backend
> bound to krb5->encrypt_name:
> 
>   BUG: KASAN: slab-use-after-free in t5_stub_complete+0x7d/0xc7
> 
> The helpers were written synchronously, so filter the async
> instances out at allocation time instead of plumbing
> crypto_wait_req() through every call site.
> 
> Reachable via net/rxrpc/rxgk.c, fs/afs/cm_security.c and
> net/ceph/crypto.c on systems with an async AEAD provider bound to
> the krb5 enctype name.
> 
> Fixes: 00244da40f78 ("crypto/krb5: Implement the Kerberos5 rfc3961 encrypt and decrypt functions")
> Fixes: 6c3c0e86c2ac ("crypto/krb5: Implement the AES enctypes from rfc8009")
> Cc: stable at vger.kernel.org
> Suggested-by: Herbert Xu <herbert at gondor.apana.org.au>
> Assisted-by: Claude:claude-opus-4-7
> Signed-off-by: Michael Bommarito <michael.bommarito at gmail.com>
> ---
>  crypto/krb5/krb5_api.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert at gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt