[nginx] Negative size buffers detection.

[Maxim Dounin]

details: https://hg.nginx.org/nginx/rev/a7ff19afbb14
branches:
changeset: 7401:a7ff19afbb14
user: Maxim Dounin <***@mdounin.ru>
date: Mon Nov 26 18:29:56 2018 +0300
description:
Negative size buffers detection.

In the past, there were several security issues which resulted in
worker process memory disclosure due to buffers with negative size.
It looks reasonable to check for such buffers in various places,
much like we already check for zero size buffers.

While here, removed "#if 1 / #endif" around zero size buffer checks.
It looks highly unlikely that we'll disable these checks anytime soon.

diffstat:

src/core/ngx_output_chain.c | 64 +++++++++++++++++++++++++++-
src/http/ngx_http_write_filter_module.c | 40 ++++++++++++++++-
src/stream/ngx_stream_write_filter_module.c | 40 ++++++++++++++++-
3 files changed, 132 insertions(+), 12 deletions(-)

diffs (244 lines):

diff --git a/src/core/ngx_output_chain.c b/src/core/ngx_output_chain.c
--- a/src/core/ngx_output_chain.c
+++ b/src/core/ngx_output_chain.c
@@ -126,6 +126,26 @@ ngx_output_chain(ngx_output_chain_ctx_t
continue;
}

+ if (bsize < 0) {
+
+ ngx_log_error(NGX_LOG_ALERT, ctx->pool->log, 0,
+ "negative size buf in output "
+ "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+ ctx->in->buf->temporary,
+ ctx->in->buf->recycled,
+ ctx->in->buf->in_file,
+ ctx->in->buf->start,
+ ctx->in->buf->pos,
+ ctx->in->buf->last,
+ ctx->in->buf->file,
+ ctx->in->buf->file_pos,
+ ctx->in->buf->file_last);
+
+ ngx_debug_point();
+
+ return NGX_ERROR;
+ }
+
if (ngx_output_chain_as_is(ctx, ctx->in->buf)) {

/* move the chain link to the output chain */
@@ -665,7 +685,6 @@ ngx_chain_writer(void *data, ngx_chain_t

for (size = 0; in; in = in->next) {

-#if 1
if (ngx_buf_size(in->buf) == 0 && !ngx_buf_special(in->buf)) {

ngx_log_error(NGX_LOG_ALERT, ctx->pool->log, 0,
@@ -685,7 +704,26 @@ ngx_chain_writer(void *data, ngx_chain_t

continue;
}
-#endif
+
+ if (ngx_buf_size(in->buf) < 0) {
+
+ ngx_log_error(NGX_LOG_ALERT, ctx->pool->log, 0,
+ "negative size buf in chain writer "
+ "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+ in->buf->temporary,
+ in->buf->recycled,
+ in->buf->in_file,
+ in->buf->start,
+ in->buf->pos,
+ in->buf->last,
+ in->buf->file,
+ in->buf->file_pos,
+ in->buf->file_last);
+
+ ngx_debug_point();
+
+ return NGX_ERROR;
+ }

size += ngx_buf_size(in->buf);

@@ -709,7 +747,6 @@ ngx_chain_writer(void *data, ngx_chain_t

for (cl = ctx->out; cl; cl = cl->next) {

-#if 1
if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {

ngx_log_error(NGX_LOG_ALERT, ctx->pool->log, 0,
@@ -729,7 +766,26 @@ ngx_chain_writer(void *data, ngx_chain_t

continue;
}
-#endif
+
+ if (ngx_buf_size(cl->buf) < 0) {
+
+ ngx_log_error(NGX_LOG_ALERT, ctx->pool->log, 0,
+ "negative size buf in chain writer "
+ "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+ cl->buf->temporary,
+ cl->buf->recycled,
+ cl->buf->in_file,
+ cl->buf->start,
+ cl->buf->pos,
+ cl->buf->last,
+ cl->buf->file,
+ cl->buf->file_pos,
+ cl->buf->file_last);
+
+ ngx_debug_point();
+
+ return NGX_ERROR;
+ }

size += ngx_buf_size(cl->buf);
}
diff --git a/src/http/ngx_http_write_filter_module.c b/src/http/ngx_http_write_filter_module.c
--- a/src/http/ngx_http_write_filter_module.c
+++ b/src/http/ngx_http_write_filter_module.c
@@ -80,7 +80,6 @@ ngx_http_write_filter(ngx_http_request_t
cl->buf->file_pos,
cl->buf->file_last - cl->buf->file_pos);

-#if 1
if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
ngx_log_error(NGX_LOG_ALERT, c->log, 0,
"zero size buf in writer "
@@ -98,7 +97,24 @@ ngx_http_write_filter(ngx_http_request_t
ngx_debug_point();
return NGX_ERROR;
}
-#endif
+
+ if (ngx_buf_size(cl->buf) < 0) {
+ ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+ "negative size buf in writer "
+ "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+ cl->buf->temporary,
+ cl->buf->recycled,
+ cl->buf->in_file,
+ cl->buf->start,
+ cl->buf->pos,
+ cl->buf->last,
+ cl->buf->file,
+ cl->buf->file_pos,
+ cl->buf->file_last);
+
+ ngx_debug_point();
+ return NGX_ERROR;
+ }

size += ngx_buf_size(cl->buf);

@@ -136,7 +152,6 @@ ngx_http_write_filter(ngx_http_request_t
cl->buf->file_pos,
cl->buf->file_last - cl->buf->file_pos);

-#if 1
if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
ngx_log_error(NGX_LOG_ALERT, c->log, 0,
"zero size buf in writer "
@@ -154,7 +169,24 @@ ngx_http_write_filter(ngx_http_request_t
ngx_debug_point();
return NGX_ERROR;
}
-#endif
+
+ if (ngx_buf_size(cl->buf) < 0) {
+ ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+ "negative size buf in writer "
+ "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+ cl->buf->temporary,
+ cl->buf->recycled,
+ cl->buf->in_file,
+ cl->buf->start,
+ cl->buf->pos,
+ cl->buf->last,
+ cl->buf->file,
+ cl->buf->file_pos,
+ cl->buf->file_last);
+
+ ngx_debug_point();
+ return NGX_ERROR;
+ }

size += ngx_buf_size(cl->buf);

diff --git a/src/stream/ngx_stream_write_filter_module.c b/src/stream/ngx_stream_write_filter_module.c
--- a/src/stream/ngx_stream_write_filter_module.c
+++ b/src/stream/ngx_stream_write_filter_module.c
@@ -104,7 +104,6 @@ ngx_stream_write_filter(ngx_stream_sessi
cl->buf->file_pos,
cl->buf->file_last - cl->buf->file_pos);

-#if 1
if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
ngx_log_error(NGX_LOG_ALERT, c->log, 0,
"zero size buf in writer "
@@ -122,7 +121,24 @@ ngx_stream_write_filter(ngx_stream_sessi
ngx_debug_point();
return NGX_ERROR;
}
-#endif
+
+ if (ngx_buf_size(cl->buf) < 0) {
+ ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+ "negative size buf in writer "
+ "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+ cl->buf->temporary,
+ cl->buf->recycled,
+ cl->buf->in_file,
+ cl->buf->start,
+ cl->buf->pos,
+ cl->buf->last,
+ cl->buf->file,
+ cl->buf->file_pos,
+ cl->buf->file_last);
+
+ ngx_debug_point();
+ return NGX_ERROR;
+ }

size += ngx_buf_size(cl->buf);

@@ -160,7 +176,6 @@ ngx_stream_write_filter(ngx_stream_sessi
cl->buf->file_pos,
cl->buf->file_last - cl->buf->file_pos);

-#if 1
if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
ngx_log_error(NGX_LOG_ALERT, c->log, 0,
"zero size buf in writer "
@@ -178,7 +193,24 @@ ngx_stream_write_filter(ngx_stream_sessi
ngx_debug_point();
return NGX_ERROR;
}
-#endif
+
+ if (ngx_buf_size(cl->buf) < 0) {
+ ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+ "negative size buf in writer "
+ "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+ cl->buf->temporary,
+ cl->buf->recycled,
+ cl->buf->in_file,
+ cl->buf->start,
+ cl->buf->pos,
+ cl->buf->last,
+ cl->buf->file,
+ cl->buf->file_pos,
+ cl->buf->file_last);
+
+ ngx_debug_point();
+ return NGX_ERROR;
+ }

size += ngx_buf_size(cl->buf);