CVE-2026-31533

Summary

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

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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/414fc5e5a5aff776c150f1b86770e0a25a35df3a
• https://git.kernel.org/stable/c/02f3ecadb23558bbe068e6504118f1b712d4ece0
• https://git.kernel.org/stable/c/0e43e0a3c94044acc74b8e0927c27972eb5a59e8
• https://git.kernel.org/stable/c/aa9facde6c5005205874c37db3fd25799d741baf
• https://git.kernel.org/stable/c/5d70eb25b41e9b010828cd12818b06a0c3b04412
• https://git.kernel.org/stable/c/2694d408b0e595024e0fc1d64ff9db0358580f74
• https://git.kernel.org/stable/c/a9b8b18364fffce4c451e6f6fd218fa4ab646705

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