printf-hook-builtin: Fix invalid memory access
When precision is given for a string, we must not run unbounded strlen() as it will read beyond the given length. It might even cause a crash if the given pointer is near end of heap or mapping. Fixes numerous valgrind errors such as: ==19215== Invalid read of size 1 ==19215== at 0x52D36C6: builtin_vsnprintf (printf_hook_builtin.c:853) ==19215== by 0x52D40A8: builtin_snprintf (printf_hook_builtin.c:1084) ==19215== by 0x52CE464: dntoa (identification.c:337) ==19215== by 0x52CE464: identification_printf_hook (identification.c:837) ==19215== by 0x52D3DAA: builtin_vsnprintf (printf_hook_builtin.c:1010) ==19215== by 0x57040EB: vlog (bus.c:388) ==19215== by 0x570427D: log_ (bus.c:430) ==19215== by 0xA8445D3: load_x509_ca (stroke_cred.c:416) ==19215== by 0xA8445D3: load_certdir (stroke_cred.c:537) ==19215== by 0xA846A95: load_certs (stroke_cred.c:1353) ==19215== by 0xA846A95: stroke_cred_create (stroke_cred.c:1475) ==19215== by 0xA84073E: stroke_socket_create (stroke_socket.c:782) ==19215== by 0xA83F27C: register_stroke (stroke_plugin.c:53) ==19215== by 0x52C3125: load_feature (plugin_loader.c:716) ==19215== by 0x52C3125: load_provided (plugin_loader.c:778) ==19215== by 0x52C3A20: load_features (plugin_loader.c:799) ==19215== by 0x52C3A20: load_plugins (plugin_loader.c:1159) ==19215== Address 0x50cdb42 is 0 bytes after a block of size 2 alloc'd ==19215== at 0x4C919FE: malloc (vg_replace_malloc.c:296) ==19215== by 0x52CD198: chunk_printable (chunk.c:759) ==19215== by 0x52CE442: dntoa (identification.c:334) ==19215== by 0x52CE442: identification_printf_hook (identification.c:837) ==19215== by 0x52D3DAA: builtin_vsnprintf (printf_hook_builtin.c:1010) ==19215== by 0x57040EB: vlog (bus.c:388) ==19215== by 0x570427D: log_ (bus.c:430) ==19215== by 0xA8445D3: load_x509_ca (stroke_cred.c:416) ==19215== by 0xA8445D3: load_certdir (stroke_cred.c:537) ==19215== by 0xA846A95: load_certs (stroke_cred.c:1353) ==19215== by 0xA846A95: stroke_cred_create (stroke_cred.c:1475) ==19215== by 0xA84073E: stroke_socket_create (stroke_socket.c:782) ==19215== by 0xA83F27C: register_stroke (stroke_plugin.c:53) ==19215== by 0x52C3125: load_feature (plugin_loader.c:716) ==19215== by 0x52C3125: load_provided (plugin_loader.c:778) ==19215== by 0x52C3A20: load_features (plugin_loader.c:799) ==19215== by 0x52C3A20: load_plugins (plugin_loader.c:1159)
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197de6e66b
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7be8965225
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@ -843,7 +843,8 @@ int builtin_vsnprintf(char *buffer, size_t n, const char *format, va_list ap)
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/* String */
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sarg = va_arg(ap, const char *);
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sarg = sarg ? sarg : "(null)";
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slen = strlen(sarg);
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slen = prec != -1 ? strnlen(sarg, prec)
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: strlen(sarg);
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goto is_string;
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}
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case 'm':
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