From c8b04142078a9ccb9e402ab7c38de7123256f4a5 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Thu, 4 Jun 2026 13:05:10 -0300 Subject: [PATCH] perf sched: Fix comp_cpus heap overflow with cross-machine recordings MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit setup_map_cpus() allocates comp_cpus based on sysconf(_SC_NPROCESSORS_CONF), the host machine's CPU count. But map_switch_event() indexes comp_cpus using cpus_nr derived from bitmap_weight(comp_cpus_mask, MAX_CPUS), where comp_cpus_mask is declared as DECLARE_BITMAP(..., MAX_CPUS) with MAX_CPUS=4096. When analyzing a perf.data recording from a machine with more CPUs than the analysis host (e.g. 128-CPU server recording analyzed on an 8-CPU laptop), cpus_nr exceeds the allocation size, causing a heap buffer overflow. Also fix a type mismatch: comp_cpus is 'struct perf_cpu *' (2 bytes per element) but was allocated with sizeof(int) (4 bytes per element). Allocate comp_cpus with MAX_CPUS entries using the correct element size, matching the comp_cpus_mask bitmap bounds. Remove the sysconf(_SC_NPROCESSORS_CONF) initialization of max_cpu — its only consumer was the comp_cpus allocation, and max_cpu is dynamically updated from the recording's events during processing. Fix the non-compact path to use max_cpu.cpu + 1 as cpus_nr, converting from 0-based index to count — sysconf() returned a count which masked this off-by-one. Fixes: 99623c628f54 ("perf sched: Add compact display option") Reported-by: sashiko-bot Cc: Jiri Olsa Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-sched.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c index 36da451447b5..4aa7833cae6e 100644 --- a/tools/perf/builtin-sched.c +++ b/tools/perf/builtin-sched.c @@ -1670,7 +1670,7 @@ static int map_switch_event(struct perf_sched *sched, struct perf_sample *sampl new_cpu = true; } } else - cpus_nr = sched->max_cpu.cpu; + cpus_nr = sched->max_cpu.cpu + 1; timestamp0 = sched->cpu_last_switched[this_cpu.cpu]; sched->cpu_last_switched[this_cpu.cpu] = timestamp; @@ -3573,10 +3573,8 @@ static int perf_sched__lat(struct perf_sched *sched) static int setup_map_cpus(struct perf_sched *sched) { - sched->max_cpu.cpu = sysconf(_SC_NPROCESSORS_CONF); - if (sched->map.comp) { - sched->map.comp_cpus = calloc(sched->max_cpu.cpu, sizeof(int)); + sched->map.comp_cpus = calloc(MAX_CPUS, sizeof(*sched->map.comp_cpus)); if (!sched->map.comp_cpus) return -1; }