[PATCH net v2 0/4] rxrpc: Better fix for DATA/RESPONSE decrypt vs splice()

[David Howells <dhowells@redhat.com>]

Here are two patches containing better fixes for the in-place decryption of
DATA and RESPONSE packets that can corrupt pagecache spliced into UDP
packets and sent to an AF_RXRPC server [CVE-2026-43500], plus a patch to
precheck the length of rxgk-secured DATA packets.

[!] Note that Hyunwoo Kim's fix is included as that is a prerequisite for
the main patches to build.  This is in Linus's tree, but not yet net/main.

Of the main patches, one patch fixes DATA decryption by having recvmsg
unconditionally extract the data into a flat bounce buffer and, if need be,
decrypt it there.  It doesn't seem to cause a performance problem to do
this even on unencrypted packets; for encrypted packets it makes sure the
content is correctly aligned for crypto which seems to get a small
performance gain.

Further, it means that DATA packets are no longer copied in the I/O thread,
avoiding a slowdown of the protocol engine that runs there.

The other main patch fixes RESPONSE decryption by having the connection
event handler worker copy the data to a flat buffer and, again, decrypt it
there.  This simplifies RESPONSE handling.

With these two fixes, the data content of the received sk_buff no longer
gets altered.

David

The patches can be found here also:

	http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=rxrpc-fixes

Changes
=======
ver #2)
- In rxrpc_verify_data():
  - Flipped the order of the buffer size comparison.
  - Used max() not umin() to calculate the minimum buffer size.
- In rxrpc_verify_response(), returned -ENOMEM rather than uninitialised
  ret.
- Removed the xdr wrappers that were added to make backporting easier.
- Fixed Sashiko review comments[1]:
  - Added length prechecking of received packets secured with RxGK, thereby
    avoiding looking at an unallocated buffer.
  - Added missing crypto free.

[1] https://sashiko.dev/#/patchset/20260511160753.607296-1-dhowells%40redhat.com

David Howells (3):
  crypto/krb5, rxrpc: Fix lack of pre-decrypt/pre-verify length checks
  rxrpc: Fix DATA decrypt vs splice() by copying data to buffer in
    recvmsg
  rxrpc: Fix RESPONSE packet verification to extract skb to a linear
    buffer

Hyunwoo Kim (1):
  rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present

 Documentation/crypto/krb5.rst |  17 +++-
 crypto/krb5/krb5_api.c        |  54 ++++++++++--
 include/crypto/krb5.h         |   9 +-
 include/trace/events/rxrpc.h  |   1 +
 net/rxrpc/ar-internal.h       |  14 +--
 net/rxrpc/call_event.c        |  20 +----
 net/rxrpc/call_object.c       |   2 +
 net/rxrpc/conn_event.c        |  29 +++----
 net/rxrpc/insecure.c          |   8 +-
 net/rxrpc/recvmsg.c           |  72 +++++++++++++---
 net/rxrpc/rxgk.c              | 156 ++++++++++++++--------------------
 net/rxrpc/rxgk_app.c          |  44 ++++------
 net/rxrpc/rxgk_common.h       |  66 +++++++-------
 net/rxrpc/rxkad.c             | 115 +++++++++----------------
 14 files changed, 306 insertions(+), 301 deletions(-)