Patch "tls: fix NULL deref on tls_sw_splice_eof() with empty record" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    tls: fix NULL deref on tls_sw_splice_eof() with empty record

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tls-fix-null-deref-on-tls_sw_splice_eof-with-empty-record.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 53f2cb491b500897a619ff6abd72f565933760f0 Mon Sep 17 00:00:00 2001
From: Jann Horn <jannh@xxxxxxxxxx>
Date: Wed, 22 Nov 2023 22:44:47 +0100
Subject: tls: fix NULL deref on tls_sw_splice_eof() with empty record

From: Jann Horn <jannh@xxxxxxxxxx>

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@xxxxxxxxxxxxxxx
Reported-by: syzbot+40d43509a099ea756317@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20231122214447.675768-1-jannh@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/tls/tls_sw.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1179,11 +1179,14 @@ void tls_sw_splice_eof(struct socket *so
 	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,


Patches currently in stable-queue which might be from jannh@xxxxxxxxxx are

queue-6.1/tls-fix-null-deref-on-tls_sw_splice_eof-with-empty-record.patch




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