tls: fix use after free in tls_sk_proto_close

syzbot reported a use-after-free in tls_sk_proto_close

Add a boolean value to cleanup a bit this function.

BUG: KASAN: use-after-free in tls_sk_proto_close+0x8ab/0x9c0 net/tls/tls_main.c:297
Read of size 1 at addr ffff8801ae40a858 by task syz-executor363/4503

CPU: 0 PID: 4503 Comm: syz-executor363 Not tainted 4.17.0-rc3+ #34
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1b9/0x294 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
 tls_sk_proto_close+0x8ab/0x9c0 net/tls/tls_main.c:297
 inet_release+0x104/0x1f0 net/ipv4/af_inet.c:427
 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:460
 sock_release+0x96/0x1b0 net/socket.c:594
 sock_close+0x16/0x20 net/socket.c:1149
 __fput+0x34d/0x890 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0x1e4/0x290 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x1aee/0x2730 kernel/exit.c:865
 do_group_exit+0x16f/0x430 kernel/exit.c:968
 get_signal+0x886/0x1960 kernel/signal.c:2469
 do_signal+0x98/0x2040 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
 do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4457b9
RSP: 002b:00007fdf4d766da8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00000000006dac3c RCX: 00000000004457b9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000006dac3c
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac38
R13: 3692738801137283 R14: 6bf92c39443c4c1d R15: 0000000000000006

Allocated by task 4498:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
 kmalloc include/linux/slab.h:512 [inline]
 kzalloc include/linux/slab.h:701 [inline]
 create_ctx net/tls/tls_main.c:521 [inline]
 tls_init+0x1f9/0xb00 net/tls/tls_main.c:633
 tcp_set_ulp+0x1bc/0x520 net/ipv4/tcp_ulp.c:153
 do_tcp_setsockopt.isra.39+0x44a/0x2600 net/ipv4/tcp.c:2588
 tcp_setsockopt+0xc1/0xe0 net/ipv4/tcp.c:2893
 sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3039
 __sys_setsockopt+0x1bd/0x390 net/socket.c:1903
 __do_sys_setsockopt net/socket.c:1914 [inline]
 __se_sys_setsockopt net/socket.c:1911 [inline]
 __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1911
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4503:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kfree+0xd9/0x260 mm/slab.c:3813
 tls_sw_free_resources+0x2a3/0x360 net/tls/tls_sw.c:1037
 tls_sk_proto_close+0x67c/0x9c0 net/tls/tls_main.c:288
 inet_release+0x104/0x1f0 net/ipv4/af_inet.c:427
 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:460
 sock_release+0x96/0x1b0 net/socket.c:594
 sock_close+0x16/0x20 net/socket.c:1149
 __fput+0x34d/0x890 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0x1e4/0x290 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x1aee/0x2730 kernel/exit.c:865
 do_group_exit+0x16f/0x430 kernel/exit.c:968
 get_signal+0x886/0x1960 kernel/signal.c:2469
 do_signal+0x98/0x2040 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
 do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801ae40a800
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 88 bytes inside of
 256-byte region [ffff8801ae40a800, ffff8801ae40a900)
The buggy address belongs to the page:
page:ffffea0006b90280 count:1 mapcount:0 mapping:ffff8801ae40a080 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801ae40a080 0000000000000000 000000010000000c
raw: ffffea0006bea9e0 ffffea0006bc94a0 ffff8801da8007c0 0000000000000000
page dumped because: kasan: bad access detected

Fixes: dd0bed1665d6 ("tls: support for Inline tls record")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Atul Gupta <atul.gupta@chelsio.com>
Cc: Steve Wise <swise@opengridcomputing.com>
Cc: Ilya Lesokhin <ilyal@mellanox.com>
Cc: Aviad Yehezkel <aviadye@mellanox.com>
Cc: Dave Watson <davejwatson@fb.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tls/tls_main.c

@@ -248,16 +248,13 @@ static void tls_sk_proto_close(struct sock *sk, long timeout)
 	struct tls_context *ctx = tls_get_ctx(sk);
 	long timeo = sock_sndtimeo(sk, 0);
 	void (*sk_proto_close)(struct sock *sk, long timeout);
+	bool free_ctx = false;
 
 	lock_sock(sk);
 	sk_proto_close = ctx->sk_proto_close;
 
-	if (ctx->conf == TLS_HW_RECORD)
-		goto skip_tx_cleanup;
-
-	if (ctx->conf == TLS_BASE) {
-		kfree(ctx);
-		ctx = NULL;
+	if (ctx->conf == TLS_BASE || ctx->conf == TLS_HW_RECORD) {
+		free_ctx = true;
 		goto skip_tx_cleanup;
 	}
 
@@ -294,7 +291,7 @@ skip_tx_cleanup:
 	/* free ctx for TLS_HW_RECORD, used by tcp_set_state
 	 * for sk->sk_prot->unhash [tls_hw_unhash]
 	 */
-	if (ctx && ctx->conf == TLS_HW_RECORD)
+	if (free_ctx)
 		kfree(ctx);
 }