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 6.6-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-6.6 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(+)
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,
--
2.43.0
Patches currently in stable-queue which might be from jannh@xxxxxxxxxx are
queue-6.6/tls-fix-null-deref-on-tls_sw_splice_eof-with-empty-record.patch
