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@@ -139,10 +139,18 @@ static INLINE char *format_msg(char *buf, size_t buf_len,
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r = tor_vsnprintf(buf+n,buf_len-n,format,ap);
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if (r < 0) {
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- n = buf_len-2; /* XXX is this line redundant with the -=2 above,
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- and also a source of underflow danger? */
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- strlcpy(buf+buf_len-TRUNCATED_STR_LEN-1, TRUNCATED_STR,
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- buf_len-(buf_len-TRUNCATED_STR_LEN-1));
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+ /* The message was too long; overwrite the end of the buffer with
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+ * "[...truncated]" */
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+ if (buf_len >= TRUNCATED_STR_LEN) {
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+ /* This is safe, since we have an extra character after buf_len
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+ to hold the \0. */
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+ strlcpy(buf+buf_len-TRUNCATED_STR_LEN, TRUNCATED_STR,
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+ buf_len-(buf_len-TRUNCATED_STR_LEN-1));
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+ }
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+ /* Set 'n' to the end of the buffer, where we'll be writing \n\0.
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+ * Since we already subtracted 2 from buf_len, this is safe.*/
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+ n = buf_len;
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+
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} else {
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n += r;
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}
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