CVE-2026-64026

In the Linux kernel, the following vulnerability has been resolved:

rxrpc: Fix DATA decrypt vs splice() by copying data to buffer in recvmsg

This improves the fix for CVE-2026-43500.

Fix the pagecache corruption from in-place decryption of a DATA packet

transmitted locally by splice() by getting rid of the packet sharing in the

I/O thread and unconditionally extracting the packet content into a bounce

buffer in which the buffer is decrypted. recvmsg() (or the kernel

equivalent) then copies the data from the bounce buffer to the destination

buffer. The sk_buff then remains unmodified.

This has an additional advantage in that the packet is then arranged in the

buffer with the correct alignment required for the crypto algorithms to

process directly. The performance of the crypto does seem to be a little

faster and, surprisingly, the unencrypted performance doesn't seem to

change much - possibly due to removing complexity from the I/O thread.

Yet another advantage is that the I/O thread doesn't have to copy packets

which would slow down packet distribution, ACK generation, etc..

The buffer belongs to the call and is allocated initially at 2K,

sufficiently large to hold a whole jumbo subpacket, but the buffer will be

increased in size if needed. However, to take this work, MSG_PEEK may

cause a later packet to be decrypted into the buffer, in which case the

earlier one will need re-decrypting for a subsequent recvmsg().

Note that rx_pkt_offset may legitimately see 0 as a valid offset now, so

switch to using USHRT_MAX to indicate an invalid offset.

Note also that I would generally prefer to replace the buffers of the

current sk_buff with a new kmalloc'd buffer of the right size, ditching the

old data and frags as this makes the handling of MSG_PEEK easier and

removes the re-decryption issue, but this looks like quite a complicated

thing to achieve. skb_morph() looks half way to what I want, but I don't

want to have to allocate a new sk_buff.