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buf_read_from_tls: Return ERROR_MISC, not WANTWRITE, on BUG().

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Fixes bug 32673; bugfix on 0.3.0.4-alpha.  We introduced these
checks in ee5471f9aa to help diagnose 21369, but we used "-1"
when "TOR_TLS_ERROR_MISC" would have been correct.  Found by opara.

I don't think that this is actually getting triggered in the wild,
but if it were, it could cause nasty behavior: spurious
WANTREAD/WANTWRITE returns have a way of turning into CPU-eating
busy-loops.
This commit is contained in:
Nick Mathewson 2020-01-29 08:49:01 -05:00
parent 19954cffd7
commit 2985a6018f
2 changed files with 7 additions and 2 deletions
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5
changes/bug32673 Normal file
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@ -0,0 +1,5 @@
o Minor bugfixes (TLS bug handling):
- When encountering a bug in buf_read_freom_tls(), return a
"MISC" error code rather than "WANTWRITE". This change might
help avoid some CPU-wasting loops if the bug is ever triggered.
Bug reported by opara. Fixes bug 32673; bugfix on 0.3.0.4-alpha.

4
src/lib/tls/buffers_tls.c
View File

@ -69,9 +69,9 @@ buf_read_from_tls(buf_t *buf, tor_tls_t *tls, size_t at_most)
check_no_tls_errors();
IF_BUG_ONCE(buf->datalen >= INT_MAX)
return -1;
return TOR_TLS_ERROR_MISC;
IF_BUG_ONCE(buf->datalen >= INT_MAX - at_most)
return -1;
return TOR_TLS_ERROR_MISC;
while (at_most > total_read) {
size_t readlen = at_most - total_read;