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Merge branch '3549-isc-resource-ub' into 'main'

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Avoid signed integer overflow in isc_resource_setlimit()

Closes #3549

See merge request isc-projects/bind9!6788
This commit is contained in:
Tony Finch 2022-10-03 11:38:20 +00:00
commit 34605e9772
1 changed files with 8 additions and 18 deletions
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26
lib/isc/resource.c
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@ -107,26 +107,16 @@ isc_resource_setlimit(isc_resource_t resource, isc_resourcevalue_t value) {
rlim_value = RLIM_INFINITY;
} else {
/*
* isc_resourcevalue_t was chosen as an unsigned 64 bit
* integer so that it could contain the maximum range of
* reasonable values. Unfortunately, this exceeds the typical
* range on Unix systems. Ensure the range of
* rlim_t is not overflowed.
* Carefully ensure the range of rlim_t is not overflowed, by
* calculating how many bytes wider is isc_resourcevalue_t than
* rlim_t, and whether rlim_t has a sign bit.
*/
isc_resourcevalue_t rlim_max;
bool rlim_t_is_signed = (((double)(rlim_t)-1) < 0);
isc_resourcevalue_t rlim_max = UINT64_MAX;
size_t wider = sizeof(rlim_max) - sizeof(rlim_t);
bool sign_bit = (double)(rlim_t)-1 < 0;
if (rlim_t_is_signed) {
rlim_max = ~((rlim_t)1 << (sizeof(rlim_t) * 8 - 1));
} else {
rlim_max = (rlim_t)-1;
}
if (value > rlim_max) {
value = rlim_max;
}
rlim_value = value;
rlim_max >>= CHAR_BIT * wider + (sign_bit ? 1 : 0);
rlim_value = ISC_MIN(value, rlim_max);
}
rl.rlim_cur = rl.rlim_max = rlim_value;