perf sched stats: Fix segmentation faults, memory leaks, and stale pointers in diff mode

The patch addresses multiple segmentation fault vectors, out-of-bounds
reads, and memory leaks in perf sched stats by adding bounds checks,
NULL checks, proper error propagation, and robust memory cleanup.

1. In get_all_cpu_stats(), added assert(!list_empty(head)) to prevent
   unsafe list_first_entry() calls on empty lists, added a missing NULL
   check for summary_head->cpu_data allocation, and implemented a cleanup
   ladder using a temporary list to prevent memory leaks on error paths.

2. In free_schedstat(), fixed memory leaks by ensuring internal domain_data
   and cpu_data pointers are freed.

3. In show_schedstat_data(), fixed a stale pointer issue where ds2 retained
   its value from a previous iteration when dptr2 became NULL, and added
   proper propagation of errors from get_all_cpu_stats().

4. Propagated show_schedstat_data() errors up to perf_sched__schedstat_diff()
   and perf_sched__schedstat_live() to prevent output corruption on failure.

5. In show_schedstat_data(), added NULL checks for cd_map1 and cd_map2
   to gracefully handle invalid or empty data files.

6. Added parallel iteration termination checks using list_is_last() in
   show_schedstat_data() for both domain and CPU lists to safely terminate
   at the end of each list when files contain a different number of CPUs
   or domains.

7. Added CPU bounds checks (cs1->cpu >= nr1 and cs2->cpu >= nr2) in
   show_schedstat_data() to prevent out-of-bounds reads from cd_map1 and
   cd_map2 when comparing files from machines with different CPU counts.

8. Added NULL checks for cd_info1 and cd_info2 to prevent crashes when
   a CPU has data samples but no corresponding domain info in the header.

9. Added domain bounds checks (ds1->domain >= cd_info1->nr_domains and
   ds2->domain >= cd_info2->nr_domains) to prevent out-of-bounds array
   accesses in the domains array.

10. Added NULL checks for dinfo1 and dinfo2 in show_schedstat_data()
    to prevent crashes when a domain has no corresponding domain info.

11. Zero-initialized the perf_data array in perf_sched__schedstat_diff()
    to prevent stack garbage from causing perf_data_file__fd() to attempt
    to use a NULL fptr when use_stdio happened to be non-zero.

Assisted-by: Gemini:gemini-3.1-pro-preview
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Athira Rajeev <atrajeev@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

0 files changed, 0 insertions, 0 deletions