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HTTP/2: avoid left-shifting signed integer into the sign bit.
On non-aligned platforms, properly cast argument before left-shifting it in
ngx_http_v2_parse_uint32 that is used with u_char. Otherwise it propagates
to int to hold the value and can step over the sign bit. Usually, on known
compilers, this results in negation. Furthermore, a subsequent store into a
wider type, that is ngx_uint_t on 64-bit platforms, results in sign-extension.
In practice, this can be observed in debug log as a very large exclusive bit
value, when client sent PRIORITY frame with exclusive bit set:
: *14 http2 PRIORITY frame sid:5 on 1 excl:8589934591 weight:17
Found with UndefinedBehaviorSanitizer.
author | Sergey Kandaurov <pluknet@nginx.com> |
---|---|
date | Thu, 07 Jul 2016 21:03:21 +0300 |
parents | 05c894a598ea |
children | 549b13cd793b |
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# Copyright (C) Igor Sysoev # Copyright (C) Nginx, Inc. NGX_MAKEFILE=$NGX_OBJS/Makefile NGX_MODULES_C=$NGX_OBJS/ngx_modules.c NGX_AUTO_HEADERS_H=$NGX_OBJS/ngx_auto_headers.h NGX_AUTO_CONFIG_H=$NGX_OBJS/ngx_auto_config.h NGX_AUTOTEST=$NGX_OBJS/autotest NGX_AUTOCONF_ERR=$NGX_OBJS/autoconf.err # STUBs NGX_ERR=$NGX_OBJS/autoconf.err MAKEFILE=$NGX_OBJS/Makefile NGX_PCH= NGX_USE_PCH= # check the echo's "-n" option and "\c" capability if echo "test\c" | grep c >/dev/null; then if echo -n test | grep n >/dev/null; then ngx_n= ngx_c= else ngx_n=-n ngx_c= fi else ngx_n= ngx_c='\c' fi # create Makefile cat << END > Makefile default: build clean: rm -rf Makefile $NGX_OBJS END