Date: Mon, 25 May 2015 18:46:29 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: ppc soft-float regression On Mon, May 25, 2015 at 05:45:12PM -0400, Rich Felker wrote: > @@ -74,6 +77,16 @@ void _dlstart_c(size_t *sp, size_t *dynv) > *rel_addr = (size_t)base + rel; > } > > + /* Prepare storage for stages 2 to save clobbered REL > + * addends so they can be reused in stage 3. There should > + * be very few. If something goes wrong and there are a > + * huge number, pass a null pointer to trigger stage 2 > + * to abort instead of risking stack overflow. */ > + int too_many_addends = symbolic_rel_cnt > 4096; > + size_t naddends = too_many_addends ? 1 : symbolic_rel_cnt; > + size_t addends[naddends]; > + size_t *paddends = too_many_addends ? 0 : addends; > + > const char *strings = (void *)(base + dyn[DT_STRTAB]); > const Sym *syms = (void *)(base + dyn[DT_SYMTAB]); This logic could lead to a zero-sized VLA (thus UB); instead, trying: int too_many_addends = symbolic_rel_cnt > 4096; size_t naddends = too_many_addends ? 0 : symbolic_rel_cnt; size_t addends[naddends+1]; size_t *paddends = too_many_addends ? 0 : addends; Avoiding the wasteful +1 would involve more conditionals so I think it's best just avoiding it. Alternatively this might be simpler/smaller: size_t addends[symbolic_rel_cnt & LIMIT-1 | 1]; size_t *paddends = symbolic_rel_cnt >= LIMIT ? 0 : addends; Rich
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