Re: [PATCH v2] perf: prevent overflow in size calculation

From: Cody P Schafer
Date: Thu Jul 19 2012 - 22:57:30 EST



struct annotation *notes = symbol__annotation(sym);
const size_t size = symbol__size(sym);
- size_t sizeof_sym_hist = (sizeof(struct sym_hist) + size * sizeof(u64));
+ size_t sizeof_sym_hist;
+
+ /* Check for overflow when calculating sizeof_sym_hist */
+ if (size > (SIZE_MAX / sizeof(u64) - sizeof(struct sym_hist)))
+ return -1;
+
+ sizeof_sym_hist = (sizeof(struct sym_hist) + size * sizeof(u64));
+
+ /* Check for overflow in zalloc argument */
+ if (sizeof_sym_hist > (SIZE_MAX / symbol_conf.nr_events
+ - sizeof(*notes->src)))
+ return -1;

notes->src = zalloc(sizeof(*notes->src) + symbol_conf.nr_events * sizeof_sym_hist);
if (notes->src == NULL)


Actually, I don't think this is correct either (subtraction seems to occur in the wrong spot).

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