net/tls: race causes kernel panic

BUG: kernel NULL pointer dereference, address: 00000000000000b8
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 80000008b6fef067 P4D 80000008b6fef067 PUD 8b6fe6067 PMD 0
 Oops: 0000 [#1] SMP PTI
 CPU: 12 PID: 23871 Comm: kworker/12:80 Kdump: loaded Tainted: G S
 5.9.0-rc3+ #1
 Hardware name: Supermicro X10SRA-F/X10SRA-F, BIOS 2.1 03/29/2018
 Workqueue: events tx_work_handler [tls]
 RIP: 0010:tx_work_handler+0x1b/0x70 [tls]
 Code: dc fe ff ff e8 16 d4 a3 f6 66 0f 1f 44 00 00 0f 1f 44 00 00 55 53 48 8b
 6f 58 48 8b bd a0 04 00 00 48 85 ff 74 1c 48 8b 47 28 <48> 8b 90 b8 00 00 00 83
 e2 02 75 0c f0 48 0f ba b0 b8 00 00 00 00
 RSP: 0018:ffffa44ace61fe88 EFLAGS: 00010286
 RAX: 0000000000000000 RBX: ffff91da9e45cc30 RCX: dead000000000122
 RDX: 0000000000000001 RSI: ffff91da9e45cc38 RDI: ffff91d95efac200
 RBP: ffff91da133fd780 R08: 0000000000000000 R09: 000073746e657665
 R10: 8080808080808080 R11: 0000000000000000 R12: ffff91dad7d30700
 R13: ffff91dab6561080 R14: 0ffff91dad7d3070 R15: ffff91da9e45cc38
 FS:  0000000000000000(0000) GS:ffff91dad7d00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00000000000000b8 CR3: 0000000906478003 CR4: 00000000003706e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  process_one_work+0x1a7/0x370
  worker_thread+0x30/0x370
  ? process_one_work+0x370/0x370
  kthread+0x114/0x130
  ? kthread_park+0x80/0x80
  ret_from_fork+0x22/0x30

tls_sw_release_resources_tx() waits for encrypt_pending, which
can have race, so we need similar changes as in commit
0cada332 here as well.

Fixes: a42055e8 ("net/tls: Add support for async encryption of records for performance")
Signed-off-by: Rohit Maheshwari <rohitm@chelsio.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tls/tls_sw.c

@@ -2143,10 +2143,15 @@ void tls_sw_release_resources_tx(struct sock *sk)
 	struct tls_context *tls_ctx = tls_get_ctx(sk);
 	struct tls_sw_context_tx *ctx = tls_sw_ctx_tx(tls_ctx);
 	struct tls_rec *rec, *tmp;
+	int pending;
 
 	/* Wait for any pending async encryptions to complete */
-	smp_store_mb(ctx->async_notify, true);
-	if (atomic_read(&ctx->encrypt_pending))
+	spin_lock_bh(&ctx->encrypt_compl_lock);
+	ctx->async_notify = true;
+	pending = atomic_read(&ctx->encrypt_pending);
+	spin_unlock_bh(&ctx->encrypt_compl_lock);
+
+	if (pending)
 		crypto_wait_req(-EINPROGRESS, &ctx->async_wait);
 
 	tls_tx_records(sk, -1);