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divzero_run_output.txt

@@ -0,0 +1 @@
+H5HF__dtable_lookup: off / start_block_size = 100 / 0 -> 

poc_fractalheap_divzero.c

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+/* Isolated reproduction of bug #2: division by zero in H5HF__dtable_lookup (H5HFdtable.c:149)
+ * if start_block_size == 0 (attacker-controlled, read raw from the file). */
+#include <stdio.h>
+
+int main(void) {
+    unsigned malicious_start_block_size = 0; /* read raw from a malicious fractal-heap header */
+    unsigned off = 100;                       /* any offset within what would be the first row */
+    printf("H5HF__dtable_lookup: off / start_block_size = %u / %u -> ", off, malicious_start_block_size);
+    fflush(stdout);
+    unsigned col = off / malicious_start_block_size; /* H5HFdtable.c:149, SIGFPE on x86 for integer division by zero */
+    printf("%u (unreachable if division by zero traps, as it does on x86)\n", col);
+    return 0;
+}