perf dso: Extra validity checks that e_machine is valid

Better ensure a read e_machine is valid by checking the file appears
like an ELF file and the read e_machine value is less than EM_NUM.

This better avoids spurious e_machine values when looking for an
e_machine in say a thread.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Aditya Bodkhe <aditya.b1@linux.ibm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.ibm.com>
Cc: Chun-Tse Shao <ctshao@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Dr. David Alan Gilbert <linux@treblig.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Haibo Xu <haibo1.xu@intel.com>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Krzysztof Łopatowski <krzysztof.m.lopatowski@gmail.com>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Mark Wielaard <mark@klomp.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergei Trofimovich <slyich@gmail.com>
Cc: Shimin Guo <shimin.guo@skydio.com>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Thomas Falcon <thomas.falcon@intel.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 18e656712f5aba14748cad613a595e7cc91c73e2..143720d1ecb158d1447ec981643eae39fcdd0ee7 100644 (file)
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -1236,17 +1236,28 @@ uint16_t dso__e_machine(struct dso *dso, struct machine *machine)
        try_to_open_dso(dso, machine);
        fd = dso__data(dso)->fd;
        if (fd >= 0) {
-               _Static_assert(offsetof(Elf32_Ehdr, e_machine) == 18, "Unexpected offset");
-               _Static_assert(offsetof(Elf64_Ehdr, e_machine) == 18, "Unexpected offset");
-               if (dso__needs_swap(dso) == DSO_SWAP__UNSET) {
-                       unsigned char eidata;
-
-                       if (pread(fd, &eidata, sizeof(eidata), EI_DATA) == sizeof(eidata))
-                               dso__swap_init(dso, eidata);
+               unsigned char e_ident[EI_NIDENT];
+
+               _Static_assert(offsetof(Elf32_Ehdr, e_ident) == 0, "Unexpected offset");
+               _Static_assert(offsetof(Elf64_Ehdr, e_ident) == 0, "Unexpected offset");
+               if (pread(fd, &e_ident, sizeof(e_ident), 0) == sizeof(e_ident) &&
+                   memcmp(e_ident, ELFMAG, SELFMAG) == 0 &&
+                   e_ident[EI_CLASS] > ELFCLASSNONE && e_ident[EI_CLASS] < ELFCLASSNUM &&
+                   e_ident[EI_DATA] > ELFDATANONE && e_ident[EI_DATA] < ELFDATANUM &&
+                   e_ident[EI_VERSION] == EV_CURRENT) {
+                       _Static_assert(offsetof(Elf32_Ehdr, e_machine) == 18, "Unexpected offset");
+                       _Static_assert(offsetof(Elf64_Ehdr, e_machine) == 18, "Unexpected offset");
+
+                       if (dso__needs_swap(dso) == DSO_SWAP__UNSET)
+                               dso__swap_init(dso, e_ident[EI_DATA]);
+
+                       if (dso__needs_swap(dso) != DSO_SWAP__UNSET &&
+                           pread(fd, &e_machine, sizeof(e_machine), 18) == sizeof(e_machine) &&
+                           e_machine < EM_NUM)
+                               e_machine = DSO__SWAP(dso, uint16_t, e_machine);
+                       else
+                               e_machine = EM_NONE;
                }
-               if (dso__needs_swap(dso) != DSO_SWAP__UNSET &&
-                   pread(fd, &e_machine, sizeof(e_machine), 18) == sizeof(e_machine))
-                       e_machine = DSO__SWAP(dso, uint16_t, e_machine);
        }
        mutex_unlock(dso__data_open_lock());
        return e_machine;