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git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
tools/sched_ext: scx_flatcg: fix potential stack overflow from VLA in fcg_read_stats
fcg_read_stats() had a VLA allocating 21 * nr_cpus * 8 bytes on the
stack, risking stack overflow on large CPU counts (nr_cpus can be up
to 512).
Fix by using a single heap allocation with the correct size, reusing
it across all stat indices, and freeing it at the end.
Signed-off-by: David Carlier <devnexen@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
authored by
David Carlier
and committed by
Tejun Heo
cabd76bb
0b82cc33
+9
-4
+9
-4
tools/sched_ext/scx_flatcg.c
+9
-4
tools/sched_ext/scx_flatcg.c
···
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static void fcg_read_stats(struct scx_flatcg *skel, __u64 *stats)
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{
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-
__u64 cnts[FCG_NR_STATS][skel->rodata->nr_cpus];
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+
__u64 *cnts;
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__u32 idx;
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cnts = calloc(skel->rodata->nr_cpus, sizeof(__u64));
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if (!cnts)
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return;
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+
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memset(stats, 0, sizeof(stats[0]) * FCG_NR_STATS);
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memset(cnts, 0, sizeof(cnts));
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for (idx = 0; idx < FCG_NR_STATS; idx++) {
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int ret, cpu;
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ret = bpf_map_lookup_elem(bpf_map__fd(skel->maps.stats),
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&idx, cnts[idx]);
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&idx, cnts);
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if (ret < 0)
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continue;
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for (cpu = 0; cpu < skel->rodata->nr_cpus; cpu++)
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stats[idx] += cnts[idx][cpu];
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stats[idx] += cnts[cpu];
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}
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free(cnts);
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}
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int main(int argc, char **argv)