[SRU][J/N/Q][PATCH 0/1] CVE-2026-31533

[Tim Whisonant]

SRU Justification:

[Impact]

net/tls: fix use-after-free in -EBUSY error path of tls_do_encryption

The -EBUSY handling in tls_do_encryption(), introduced by commit
859054147318 ("net: tls: handle backlogging of crypto requests"), has
a use-after-free due to double cleanup of encrypt_pending and the
scatterlist entry.

When crypto_aead_encrypt() returns -EBUSY, the request is enqueued to
the cryptd backlog and the async callback tls_encrypt_done() will be
invoked upon completion. That callback unconditionally restores the
scatterlist entry (sge->offset, sge->length) and decrements
ctx->encrypt_pending. However, if tls_encrypt_async_wait() returns an
error, the synchronous error path in tls_do_encryption() performs the
same cleanup again, double-decrementing encrypt_pending and
double-restoring the scatterlist.

The double-decrement corrupts the encrypt_pending sentinel (initialized
to 1), making tls_encrypt_async_wait() permanently skip the wait for
pending async callbacks. A subsequent sendmsg can then free the
tls_rec via bpf_exec_tx_verdict() while a cryptd callback is still
pending, resulting in a use-after-free when the callback fires on the
freed record.

Fix this by skipping the synchronous cleanup when the -EBUSY async
wait returns an error, since the callback has already handled
encrypt_pending and sge restoration.

[Fix]

Resolute: not affected
Questing: applied Jammy patch
Noble:    applied Jammy patch
Jammy:    cherry picked from upstream
Focal:    sent to forgejo
Bionic:   not affected
Xenial:   not affected
Trusty:   not affected

[Test Plan]

Compile and boot tested.

[Where problems could occur]

The change affects the main encryption function for software-
based kernel TLS in order to correct a use-after-free. Issues
might manifest as failed or aborted encryption requests.

Muhammad Alifa Ramdhan (1):
  net/tls: fix use-after-free in -EBUSY error path of tls_do_encryption

 net/tls/tls_sw.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

-- 
2.43.0