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log: fix potential overflow with long log messages #490

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Jul 20, 2023
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log: fix potential overflow with long log messages #490

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4 changes: 2 additions & 2 deletions lib/log_blackbox.c
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Original file line number Diff line number Diff line change
Expand Up @@ -110,8 +110,8 @@ _blackbox_vlogger(int32_t target,
chunk += sizeof(uint32_t);

/* log message */
msg_len = qb_vsnprintf_serialize(chunk, max_size, cs->format, ap);
if (msg_len >= max_size) {
msg_len = qb_vsnprintf_serialize(chunk, t->max_line_length, cs->format, ap);
if (msg_len >= t->max_line_length) {
chunk = msg_len_pt + sizeof(uint32_t); /* Reset */

/* Leave this at QB_LOG_MAX_LEN so as not to overflow the blackbox */
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FYI, the next line could theoretically be a problem if the caller used QB_LOG_CONF_MAX_LINE_LEN to set the max line length below the length of the "too long" message. (I wouldn't consider it a security issue since the message is hardcoded, not to mention it would be bizarre for a caller to do that). In any case, the "too long" message isn't really helpful -- why not just use as much of the long message as possible (maybe replacing the last three usable characters with an ellipsis)?

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+1 for replacing "too long" message with shortened version of logged message. Also I think it may make sense to check QB_LOG_CONF_MAX_LINE_LEN for some minimal reasonable length (right now only maximum length of QB_LOG_ABSOLUTE_MAX_LEN is checked)

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6 changes: 4 additions & 2 deletions tests/check_log.c
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Expand Up @@ -832,8 +832,10 @@ START_TEST(test_log_long_msg)
qb_log(LOG_INFO, "Message %d %d - %s", lpc, lpc%600, buffer);
}

qb_log_blackbox_write_to_file("blackbox.dump");
qb_log_blackbox_print_from_file("blackbox.dump");
rc = qb_log_blackbox_write_to_file("blackbox.dump");
ck_assert_int_gt(rc, 0);
rc = qb_log_blackbox_print_from_file("blackbox.dump");
ck_assert_int_le(rc, 0);
unlink("blackbox.dump");
qb_log_fini();
}
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