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Gzip: fixed "zero size buf" alerts after ac5a741d39cf.

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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.
This commit is contained in:
Maxim Dounin 2019-07-31 17:29:00 +03:00
parent 6179b98ed5
commit 39c40428f9
1 changed files with 11 additions and 4 deletions
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15
src/http/modules/ngx_http_gzip_filter_module.c
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@ -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; 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 */ /* 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) ngx_http_gzip_ctx_t *ctx)
{ {
int rc; int rc;
ngx_buf_t *b;
ngx_chain_t *cl; ngx_chain_t *cl;
ctx->zin = ctx->zstream.total_in; ctx->zin = ctx->zstream.total_in;
@ -888,13 +889,19 @@ ngx_http_gzip_filter_deflate_end(ngx_http_request_t *r,
return NGX_ERROR; 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; cl->next = NULL;
*ctx->last_out = cl; *ctx->last_out = cl;
ctx->last_out = &cl->next; ctx->last_out = &cl->next;
ctx->out_buf->last_buf = 1;
ctx->zstream.avail_in = 0; ctx->zstream.avail_in = 0;
ctx->zstream.avail_out = 0; ctx->zstream.avail_out = 0;