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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 | 78f8ac479735 |
children | 325b3042edd6 |
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# Copyright (C) Igor Sysoev # Copyright (C) Nginx, Inc. if [ "$NGX_PLATFORM" != win32 ]; then ngx_feature="C compiler" ngx_feature_name= ngx_feature_run=yes ngx_feature_incs= ngx_feature_path= ngx_feature_libs= ngx_feature_test= . auto/feature if [ $ngx_found = no ]; then echo echo $0: error: C compiler $CC is not found echo exit 1 fi fi if [ "$CC" = cl ]; then NGX_CC_NAME=msvc echo " + using Microsoft Visual C++ compiler" elif [ "$CC" = wcl386 ]; then NGX_CC_NAME=owc echo " + using Open Watcom C compiler" elif [ "$CC" = bcc32 ]; then NGX_CC_NAME=bcc echo " + using Borland C++ compiler" elif `$CC -V 2>&1 | grep '^Intel(R) C' >/dev/null 2>&1`; then NGX_CC_NAME=icc echo " + using Intel C++ compiler" elif `$CC -v 2>&1 | grep 'gcc version' >/dev/null 2>&1`; then NGX_CC_NAME=gcc echo " + using GNU C compiler" elif `$CC -v 2>&1 | grep '\(clang\|LLVM\) version' >/dev/null 2>&1`; then NGX_CC_NAME=clang echo " + using Clang C compiler" elif `$CC -V 2>&1 | grep 'Sun C' >/dev/null 2>&1`; then NGX_CC_NAME=sunc echo " + using Sun C compiler" elif `$CC -V 2>&1 | grep '^Compaq C' >/dev/null 2>&1`; then NGX_CC_NAME=ccc echo " + using Compaq C compiler" elif `$CC -V 2>&1 | grep '^aCC: ' >/dev/null 2>&1`; then NGX_CC_NAME=acc echo " + using HP aC++ compiler" else NGX_CC_NAME=unknown fi