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 <[email protected]> --- tools/perf/util/dso.c | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c index 18e656712f5a..143720d1ecb1 100644 --- 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; -- 2.52.0.457.g6b5491de43-goog
