net/tls: fix race condition causing kernel panic

tls_sw_recvmsg() and tls_decrypt_done() can be run concurrently.
// tls_sw_recvmsg()
	if (atomic_read(&ctx->decrypt_pending))
		crypto_wait_req(-EINPROGRESS, &ctx->async_wait);
	else
		reinit_completion(&ctx->async_wait.completion);

//tls_decrypt_done()
  	pending = atomic_dec_return(&ctx->decrypt_pending);

  	if (!pending && READ_ONCE(ctx->async_notify))
  		complete(&ctx->async_wait.completion);

Consider the scenario tls_decrypt_done() is about to run complete()

	if (!pending && READ_ONCE(ctx->async_notify))

and tls_sw_recvmsg() reads decrypt_pending == 0, does reinit_completion(),
then tls_decrypt_done() runs complete(). This sequence of execution
results in wrong completion. Consequently, for next decrypt request,
it will not wait for completion, eventually on connection close, crypto
resources freed, there is no way to handle pending decrypt response.

This race condition can be avoided by having atomic_read() mutually
exclusive with atomic_dec_return(),complete().Intoduced spin lock to
ensure the mutual exclution.

Addressed similar problem in tx direction.

v1->v2:
- More readable commit message.
- Corrected the lock to fix new race scenario.
- Removed barrier which is not needed now.

Fixes: a42055e8d2c3 ("net/tls: Add support for async encryption of records for performance")
Signed-off-by: Vinay Kumar Yadav <vinay.yadav@chelsio.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/net/tls.h b/include/net/tls.h
index bf9eb4823933..18cd4f418464 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -135,6 +135,8 @@ struct tls_sw_context_tx {
 	struct tls_rec *open_rec;
 	struct list_head tx_list;
 	atomic_t encrypt_pending;
+	/* protect crypto_wait with encrypt_pending */
+	spinlock_t encrypt_compl_lock;
 	int async_notify;
 	u8 async_capable:1;
 
@@ -155,6 +157,8 @@ struct tls_sw_context_rx {
 	u8 async_capable:1;
 	u8 decrypted:1;
 	atomic_t decrypt_pending;
+	/* protect crypto_wait with decrypt_pending*/
+	spinlock_t decrypt_compl_lock;
 	bool async_notify;
 };