6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jann Horn jannh@google.com
commit 53f2cb491b500897a619ff6abd72f565933760f0 upstream.
syzkaller discovered that if tls_sw_splice_eof() is executed as part of sendfile() when the plaintext/ciphertext sk_msg are empty, the send path gets confused because the empty ciphertext buffer does not have enough space for the encryption overhead. This causes tls_push_record() to go on the `split = true` path (which is only supposed to be used when interacting with an attached BPF program), and then get further confused and hit the tls_merge_open_record() path, which then assumes that there must be at least one populated buffer element, leading to a NULL deref.
It is possible to have empty plaintext/ciphertext buffers if we previously bailed from tls_sw_sendmsg_locked() via the tls_trim_both_msgs() path. tls_sw_push_pending_record() already handles this case correctly; let's do the same check in tls_sw_splice_eof().
Fixes: df720d288dbb ("tls/sw: Use splice_eof() to flush") Cc: stable@vger.kernel.org Reported-by: syzbot+40d43509a099ea756317@syzkaller.appspotmail.com Signed-off-by: Jann Horn jannh@google.com Link: https://lore.kernel.org/r/20231122214447.675768-1-jannh@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/tls/tls_sw.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index a78e8e722409..316f76187962 100644 --- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c @@ -1232,11 +1232,14 @@ void tls_sw_splice_eof(struct socket *sock) lock_sock(sk);
retry: + /* same checks as in tls_sw_push_pending_record() */ rec = ctx->open_rec; if (!rec) goto unlock;
msg_pl = &rec->msg_plaintext; + if (msg_pl->sg.size == 0) + goto unlock;
/* Check the BPF advisor and perform transmission. */ ret = bpf_exec_tx_verdict(msg_pl, sk, false, TLS_RECORD_TYPE_DATA,