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HTTP/2: avoid left-shifting signed integer into the sign bit.

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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.
This commit is contained in:
Sergey Kandaurov 2016-07-07 21:03:21 +03:00
parent 6299f5e914
commit 586ef968f9
1 changed files with 1 additions and 1 deletions
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2
src/http/v2/ngx_http_v2.h
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@ -298,7 +298,7 @@ size_t ngx_http_v2_huff_encode(u_char *src, size_t len, u_char *dst,
#define ngx_http_v2_parse_uint16(p) ((p)[0] << 8 | (p)[1])
#define ngx_http_v2_parse_uint32(p) \
((p)[0] << 24 | (p)[1] << 16 | (p)[2] << 8 | (p)[3])
((uint32_t) (p)[0] << 24 | (p)[1] << 16 | (p)[2] << 8 | (p)[3])
#endif