Red Hat Bugzilla – Bug 1470124
_nl_load_locale_from_archive SIGFPE divide by zero
Last modified: 2017-11-19 21:57:53 EST
Description of problem: _nl_load_locale_from_archive defends incompletely against dividing by zero. Version-Release number of selected component (if applicable): glibc-2.24-59-g86ac4a7 How reproducible: every time (if particular corruption in locale archive) Steps to Reproduce: 1. Inspect code for _nl_load_locale_from_archive() 2. 3. Actual results: In glibc-2.24-59-g86ac4a7/locale/loadarchive.c near lines 277 through 282: /* Avoid division by 0 if the file is corrupted. */ if (__glibc_unlikely (head->namehash_size == 0)) goto close_and_out; idx = hval % head->namehash_size; incr = 1 + hval % (head->namehash_size - 2); The check defends against dividing by zero in the first modulo operation ('%') but not the second (on the next line). The check should be expanded to "head->namehash_size <= 2". The declaration in locarchive.h is uint32_t namehash_size; It seems to me that some heuristic such as (namehash_size >= (0xful << 28)) also is appropriate, to detect extremely unlikely large values [in this case 4,026,531,840 and larger]. Expected results: Correct defense against dividing by zero in all modulo operations ('%' operator). Additional info:
Out of curiosity, how did you encounter this bug?
(In reply to Florian Weimer from comment #1) > Out of curiosity, how did you encounter this bug? A side effect of investigating https://bugzilla.redhat.com/show_bug.cgi?id=1468778
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The problem persists in glibc-2.26-65-ga76376df7c which is the source for glibc-2.26-16.fc27.x86_64