From 39c40428f93db246a9a27e7a109413fae46e195d Mon Sep 17 00:00:00 2001 From: Maxim Dounin Date: Wed, 31 Jul 2019 17:29:00 +0300 Subject: Gzip: fixed "zero size buf" alerts after ac5a741d39cf. After ac5a741d39cf it is now possible that after zstream.avail_out reaches 0 and we allocate additional buffer, there will be no more data to put into this buffer, triggering "zero size buf" alert. Fix is to reset b->temporary flag in this case. Additionally, an optimization added to avoid allocating additional buffer in this case, by checking if last deflate() call returned Z_STREAM_END. Note that checking for Z_STREAM_END by itself is not enough to fix alerts, as deflate() can return Z_STREAM_END without producing any output if the buffer is smaller than gzip trailer. Reported by Witold Filipczyk, http://mailman.nginx.org/pipermail/nginx-devel/2019-July/012469.html. --- src/http/modules/ngx_http_gzip_filter_module.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/src/http/modules/ngx_http_gzip_filter_module.c b/src/http/modules/ngx_http_gzip_filter_module.c index 48f3dd7c7..c75169c53 100644 --- a/src/http/modules/ngx_http_gzip_filter_module.c +++ b/src/http/modules/ngx_http_gzip_filter_module.c @@ -778,7 +778,7 @@ ngx_http_gzip_filter_deflate(ngx_http_request_t *r, ngx_http_gzip_ctx_t *ctx) ctx->out_buf->last = ctx->zstream.next_out; - if (ctx->zstream.avail_out == 0) { + if (ctx->zstream.avail_out == 0 && rc != Z_STREAM_END) { /* zlib wants to output some more gzipped data */ @@ -868,6 +868,7 @@ ngx_http_gzip_filter_deflate_end(ngx_http_request_t *r, ngx_http_gzip_ctx_t *ctx) { int rc; + ngx_buf_t *b; ngx_chain_t *cl; ctx->zin = ctx->zstream.total_in; @@ -888,13 +889,19 @@ ngx_http_gzip_filter_deflate_end(ngx_http_request_t *r, return NGX_ERROR; } - cl->buf = ctx->out_buf; + b = ctx->out_buf; + + if (ngx_buf_size(b) == 0) { + b->temporary = 0; + } + + b->last_buf = 1; + + cl->buf = b; cl->next = NULL; *ctx->last_out = cl; ctx->last_out = &cl->next; - ctx->out_buf->last_buf = 1; - ctx->zstream.avail_in = 0; ctx->zstream.avail_out = 0; -- cgit