details: https://hg.nginx.org/nginx/rev/9ac0e8b9aced
branches: stable-1.14
changeset: 7410:9ac0e8b9aced
user: Maxim Dounin <mdounin@mdounin.ru>
date: Mon Jul 02 19:02:08 2018 +0300
description:
gRPC: clearing buffers in ngx_http_grpc_get_buf().

We copy input buffers to our buffers, so various flags might be
unexpectedly set in buffers returned by ngx_chain_get_free_buf().

In particular, the b->in_file flag might be set when the body was
written to a file in a different context. With sendfile enabled this
in turn might result in protocol corruption if such a buffer was reused
for a control frame.

Make sure to clear buffers and set only fields we really need to be set.

diffstat:

src/http/modules/ngx_http_grpc_module.c | 29 +++++++++++++++++------------
1 files changed, 17 insertions(+), 12 deletions(-)

diffs (57 lines):

diff --git a/src/http/modules/ngx_http_grpc_module.c b/src/http/modules/ngx_http_grpc_module.c
--- a/src/http/modules/ngx_http_grpc_module.c
+++ b/src/http/modules/ngx_http_grpc_module.c
@@ -3883,6 +3883,7 @@ ngx_http_grpc_send_window_update(ngx_htt
static ngx_chain_t *
ngx_http_grpc_get_buf(ngx_http_request_t *r, ngx_http_grpc_ctx_t *ctx)
{
+ u_char *start;
ngx_buf_t *b;
ngx_chain_t *cl;

@@ -3892,29 +3893,33 @@ ngx_http_grpc_get_buf(ngx_http_request_t
}

b = cl->buf;
-
- b->tag = (ngx_buf_tag_t) &ngx_http_grpc_body_output_filter;
- b->temporary = 1;
- b->flush = 1;
-
- if (b->start == NULL) {
+ start = b->start;
+
+ if (start == NULL) {

/*
* each buffer is large enough to hold two window update
* frames in a row
*/

- b->start = ngx_palloc(r->pool, 2 * sizeof(ngx_http_grpc_frame_t) + 8);
- if (b->start == NULL) {
+ start = ngx_palloc(r->pool, 2 * sizeof(ngx_http_grpc_frame_t) + 8);
+ if (start == NULL) {
return NULL;
}

- b->pos = b->start;
- b->last = b->start;
-
- b->end = b->start + 2 * sizeof(ngx_http_grpc_frame_t) + 8;
}

+ ngx_memzero(b, sizeof(ngx_buf_t));
+
+ b->start = start;
+ b->pos = start;
+ b->last = start;
+ b->end = start + 2 * sizeof(ngx_http_grpc_frame_t) + 8;
+
+ b->tag = (ngx_buf_tag_t) &ngx_http_grpc_body_output_filter;
+ b->temporary = 1;
+ b->flush = 1;
+
return cl;
}

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