net/tls: Fix flipped sign in tls_err_abort() calls

sk->sk_err appears to expect a positive value, a convention that ktls
doesn't always follow and that leads to memory corruption in other code.
For instance,

    [kworker]
    tls_encrypt_done(..., err=<negative error from crypto request>)
      tls_err_abort(.., err)
        sk->sk_err = err;

    [task]
    splice_from_pipe_feed
      ...
        tls_sw_do_sendpage
          if (sk->sk_err) {
            ret = -sk->sk_err;  // ret is positive

    splice_from_pipe_feed (continued)
      ret = actor(...)  // ret is still positive and interpreted as bytes
                        // written, resulting in underflow of buf->len and
                        // sd->len, leading to huge buf->offset and bogus
                        // addresses computed in later calls to actor()

Fix all tls_err_abort() callers to pass a negative error code
consistently and centralize the error-prone sign flip there, throwing in
a warning to catch future misuse and uninlining the function so it
really does only warn once.

Cc: stable@vger.kernel.org
Fixes: c46234ebb4d1e ("tls: RX path for ktls")
Reported-by: syzbot+b187b77c8474f9648fae@syzkaller.appspotmail.com
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 4 deletions

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index d5d09bd817b7..1644f8baea19 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -35,6 +35,7 @@
  * SOFTWARE.
  */
 
+#include <linux/bug.h>
 #include <linux/sched/signal.h>
 #include <linux/module.h>
 #include <linux/splice.h>
@@ -43,6 +44,14 @@
 #include <net/strparser.h>
 #include <net/tls.h>
 
+noinline void tls_err_abort(struct sock *sk, int err)
+{
+	WARN_ON_ONCE(err >= 0);
+	/* sk->sk_err should contain a positive error code. */
+	sk->sk_err = -err;
+	sk_error_report(sk);
+}
+
 static int __skb_nsg(struct sk_buff *skb, int offset, int len,
                      unsigned int recursion_level)
 {
@@ -419,7 +428,7 @@ int tls_tx_records(struct sock *sk, int flags)
 
 tx_err:
 	if (rc < 0 && rc != -EAGAIN)
-		tls_err_abort(sk, EBADMSG);
+		tls_err_abort(sk, -EBADMSG);
 
 	return rc;
 }
@@ -763,7 +772,7 @@ static int tls_push_record(struct sock *sk, int flags,
 			       msg_pl->sg.size + prot->tail_size, i);
 	if (rc < 0) {
 		if (rc != -EINPROGRESS) {
-			tls_err_abort(sk, EBADMSG);
+			tls_err_abort(sk, -EBADMSG);
 			if (split) {
 				tls_ctx->pending_open_record_frags = true;
 				tls_merge_open_record(sk, rec, tmp, orig_end);
@@ -1827,7 +1836,7 @@ int tls_sw_recvmsg(struct sock *sk,
 		err = decrypt_skb_update(sk, skb, &msg->msg_iter,
 					 &chunk, &zc, async_capable);
 		if (err < 0 && err != -EINPROGRESS) {
-			tls_err_abort(sk, EBADMSG);
+			tls_err_abort(sk, -EBADMSG);
 			goto recv_end;
 		}
 
@@ -2007,7 +2016,7 @@ ssize_t tls_sw_splice_read(struct socket *sock,  loff_t *ppos,
 		}
 
 		if (err < 0) {
-			tls_err_abort(sk, EBADMSG);
+			tls_err_abort(sk, -EBADMSG);
 			goto splice_read_end;
 		}
 		ctx->decrypted = 1;