[PATCH net-next 0/5] Consolidate FCrypt and PCBC code into net/rxrpc/

[Marc Dionne]

On Mon, Apr 27, 2026 at 11:47 PM Eric Biggers <ebiggers at kernel.org> wrote:
>
> [This series applies to v7.1-rc1 and is intended to be taken via
> net-next.  Patches 4-5 could be left for later if desired.]
>
> The FCrypt "block cipher" and the PCBC mode of operation are obsolete
> and insecure.  Since their only user is net/rxrpc/, they belong there,
> not in the crypto API.
>
> Therefore, this series removes these algorithms from the crypto API and
> replaces them with local implementations in net/rxrpc/.
>
> The local implementations are simpler too, as they avoid the crypto API
> boilerplate.
>
> I don't know how to test all the code in net/rxrpc/, but everything
> should still work.  I added a KUnit test for the crypto functions.

Giving this is a spin with afs, I get this oops during xfstests generic/011:

[   22.838773] kernel BUG at net/core/skbuff.c:2295!
[   22.843470] Oops: invalid opcode: 0000 [#1] SMP NOPTI
[   22.850243] CPU: 4 UID: 0 PID: 5869 Comm: fsstress Not tainted
7.1.0-rc1.kafs+ #89 PREEMPT(full)
[   22.853205] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.17.0-10.fc44 06/10/2025
[   22.855185] RIP: 0010:pskb_expand_head+0x2d2/0x380
...
[   22.867340] Call Trace:
[   22.867617]  <TASK>
[   22.869409]  __pskb_pull_tail+0x67/0x510
[   22.870719]  rxkad_verify_packet+0x297/0x3b0 [rxrpc]
[   22.872550]  rxrpc_recvmsg_data+0x150/0x760 [rxrpc]
[   22.875923]  rxrpc_kernel_recv_data+0x75/0x230 [rxrpc]
[   22.878500]  afs_extract_data+0x65/0x250 [kafs]
[   22.880238]  yfs_deliver_fs_fetch_data64+0x209/0x2f0 [kafs]
[   22.882017]  afs_deliver_to_call+0x60/0x5a0 [kafs]
[   22.882346]  afs_wait_for_call_to_complete+0x133/0x1f0 [kafs]
[   22.883019]  ? __pfx_default_wake_function+0x10/0x10
[   22.883445]  ? afs_wait_for_operation+0x2c/0x1c0 [kafs]
[   22.883878]  afs_wait_for_operation+0x9f/0x1c0 [kafs]
[   22.884342]  afs_do_sync_operation+0x1a/0x30 [kafs]
[   22.884632]  netfs_unbuffered_read_iter_locked+0x30f/0x6c0 [netfs]
[   22.884980]  netfs_unbuffered_read_iter+0x56/0x80 [netfs]
[   22.885266]  vfs_read+0x2e1/0x410

>From the stack this looks like a direct IO read, where the skb passed
to skb_linearize() trips on BUG_ON(skb_shared(skb)) in
pskb_expand_head.

Marc