examples: fix local socket address lengths#3601
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The udgram and ustream examples used sizeof(CONFIG_EXAMPLES_*_ADDR) as the pathname length and then added another NUL byte to the sockaddr length. That makes the maximum address length one byte larger than struct sockaddr_un, and ustream also wrote a terminator at sun_path[UNIX_PATH_MAX]. Track the pathname length with strnlen(), copy with room for the terminator, and pass sizeof(sa_family_t) + strlen(path) + 1 to the socket calls. Generated-by: OpenAI Codex Signed-off-by: Old-Ding <35417409+Old-Ding@users.noreply.github.com>
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| server.sun_family = AF_LOCAL; | ||
| strlcpy(server.sun_path, CONFIG_EXAMPLES_UDGRAM_ADDR, addrlen); | ||
| strlcpy(server.sun_path, CONFIG_EXAMPLES_UDGRAM_ADDR, addrlen + 1); |
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why change? strlcpy could ensure '\0' is terminated at the end of server.sun_path
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Summary
strnlen()sizeof(sa_family_t) + strlen(path) + 1tobind(),connect(), andsendto()Why
The examples used
sizeof(CONFIG_EXAMPLES_*_ADDR)as the pathname length and then added another NUL byte to the sockaddr length. For maximum-length paths this can make the supplied address length one byte larger thanstruct sockaddr_un.The stream example also wrote
sun_path[addrlen] = '\0'after clampingaddrlentoUNIX_PATH_MAX, which can write one byte pastsun_path.Testing
git diff --check HEAD~1..HEADgit show --stat --check --format=fuller HEADgcc,clang, orccinstalled.