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Merge remote-tracking branch 'teor/circuitstats-pareto-avoid-div-zero'

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Nick Mathewson 2014-09-29 09:48:02 -04:00
commit 2b1b1def46
2 changed files with 20 additions and 1 deletions
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5
changes/bug13290-avoid-div-zero-circuitstatus-pareto Normal file
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@ -0,0 +1,5 @@
o Minor bugfixes:
- In circuit_build_times_calculate_timeout() in circuitstats.c, avoid
dividing by zero in the pareto calculations. This traps under
clang -fsanitize=undefined-trap -fsanitize-undefined-trap-on-error.
Fixes bug 13290.

16
src/or/circuitstats.c
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@ -1085,7 +1085,21 @@ circuit_build_times_calculate_timeout(circuit_build_times_t *cbt,
tor_assert(1.0-quantile > 0);
tor_assert(cbt->Xm > 0);
ret = cbt->Xm/pow(1.0-quantile,1.0/cbt->alpha);
/* If either alpha or p are 0, we would divide by zero, yielding an
* infinite (double) result; which would be clamped to INT32_MAX.
* Instead, initialise ret to INT32_MAX, and skip over these
* potentially illegal/trapping divides by zero.
*/
ret = INT32_MAX;
if (cbt->alpha > 0) {
double p;
p = pow(1.0-quantile,1.0/cbt->alpha);
if (p > 0) {
ret = cbt->Xm/p;
}
}
if (ret > INT32_MAX) {
ret = INT32_MAX;
}