[PATCH 4.14 16/45] net/tls: Dont recursively call push_record during tls_write_space callbacks

Greg Kroah-Hartman
2018-05-18T08:15:33Z

From: Dave Watson <davejwatson@fb.com>

[ Upstream commit c212d2c7fc4736d49be102fb7a1a545cdc2f1fea ]

It is reported that in some cases, write_space may be called in
do_tcp_sendpages, such that we recursively invoke do_tcp_sendpages again:

[ 660.468802] ? do_tcp_sendpages+0x8d/0x580
[ 660.468826] ? tls_push_sg+0x74/0x130 [tls]
[ 660.468852] ? tls_push_record+0x24a/0x390 [tls]
[ 660.468880] ? tls_write_space+0x6a/0x80 [tls]
...

tls_push_sg already does a loop over all sending sg's, so ignore
any tls_write_space notifications until we are done sending.
We then have to call the previous write_space to wake up
poll() waiters after we are done with the send loop.

Reported-by: Andre Tomt <andre@tomt.net>
Signed-off-by: Dave Watson <davejwatson@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/tls.h | 1 +
net/tls/tls_main.c | 7 +++++++
2 files changed, 8 insertions(+)

--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -98,6 +98,7 @@ struct tls_context {
struct scatterlist *partially_sent_record;
u16 partially_sent_offset;
unsigned long flags;
+ bool in_tcp_sendpages;

u16 pending_open_record_frags;
int (*push_pending_record)(struct sock *sk, int flags);
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -87,6 +87,7 @@ int tls_push_sg(struct sock *sk,
size = sg->length - offset;
offset += sg->offset;

+ ctx->in_tcp_sendpages = true;
while (1) {
if (sg_is_last(sg))
sendpage_flags = flags;
@@ -121,6 +122,8 @@ retry:
}

clear_bit(TLS_PENDING_CLOSED_RECORD, &ctx->flags);
+ ctx->in_tcp_sendpages = false;
+ ctx->sk_write_space(sk);

return 0;
}
@@ -190,6 +193,10 @@ static void tls_write_space(struct sock
{
struct tls_context *ctx = tls_get_ctx(sk);

+ /* We are already sending pages, ignore notification */
+ if (ctx->in_tcp_sendpages)
+ return;
+
if (!sk->sk_write_pending && tls_is_pending_closed_record(ctx)) {
gfp_t sk_allocation = sk->sk_allocation;
int rc;