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charset="UTF-8" __machine__addnew_vdso() called __dsos__add(&machine->dsos, dso) without holding machine->dsos.lock, and machine__findnew_vdso() and __machine__findnew_compat() initialized machine->vdso_info and created temporary VDSO files without synchronization. Acquire machine->dsos.lock in write mode across machine->vdso_info initialization, duplicate checking via __dsos__find(), temporary file creation, dso__set_long_name(), and __dsos__add(). Fixes: f649ed80f3ca ("perf dsos: Tidy reference counting and locking") Signed-off-by: Ian Rogers --- tools/perf/util/dsos.c | 8 ++++++- tools/perf/util/dsos.h | 2 ++ tools/perf/util/vdso.c | 52 +++++++++++++++++++++++++++--------------- 3 files changed, 42 insertions(+), 20 deletions(-) diff --git a/tools/perf/util/dsos.c b/tools/perf/util/dsos.c index a2cd37bd1660..1574c8885d78 100644 --- a/tools/perf/util/dsos.c +++ b/tools/perf/util/dsos.c @@ -284,12 +284,18 @@ static struct dso *__dsos__find_id(struct dsos *dsos, const char *name, const st return res; } +struct dso *__dsos__find(struct dsos *dsos, const char *name, bool cmp_short, bool write_locked) + __must_hold_shared(&dsos->lock) +{ + return __dsos__find_id(dsos, name, &dso_id_empty, cmp_short, write_locked); +} + struct dso *dsos__find(struct dsos *dsos, const char *name, bool cmp_short) { struct dso *res; down_read(&dsos->lock); - res = __dsos__find_id(dsos, name, &dso_id_empty, cmp_short, /*write_locked=*/false); + res = __dsos__find(dsos, name, cmp_short, /*write_locked=*/false); up_read(&dsos->lock); return res; } diff --git a/tools/perf/util/dsos.h b/tools/perf/util/dsos.h index a26774950866..dbd06f420753 100644 --- a/tools/perf/util/dsos.h +++ b/tools/perf/util/dsos.h @@ -30,6 +30,8 @@ void dsos__exit(struct dsos *dsos); int __dsos__add(struct dsos *dsos, struct dso *dso); int dsos__add(struct dsos *dsos, struct dso *dso); +struct dso *__dsos__find(struct dsos *dsos, const char *name, bool cmp_short, bool write_locked) + __must_hold_shared(&dsos->lock); struct dso *dsos__find(struct dsos *dsos, const char *name, bool cmp_short); struct dso *dsos__findnew_id(struct dsos *dsos, const char *name, const struct dso_id *id); diff --git a/tools/perf/util/vdso.c b/tools/perf/util/vdso.c index c12f5d8c4bf6..93828e660672 100644 --- a/tools/perf/util/vdso.c +++ b/tools/perf/util/vdso.c @@ -131,8 +131,13 @@ static struct dso *__machine__addnew_vdso(struct machine *machine, const char *s dso = dso__new(short_name); if (dso != NULL) { - __dsos__add(&machine->dsos, dso); + /* + * Set the long name before adding to machine->dsos so that + * __dsos__add() inserts it in sorted order without needing to + * re-take machine->dsos.lock. + */ dso__set_long_name(dso, long_name, false); + __dsos__add(&machine->dsos, dso); } return dso; @@ -250,15 +255,19 @@ static struct dso *__machine__findnew_compat(struct machine *machine, const char *file_name; struct dso *dso; - dso = dsos__find(&machine->dsos, vdso_file->dso_name, true); + down_write(&machine->dsos.lock); + dso = __dsos__find(&machine->dsos, vdso_file->dso_name, true, /*write_locked=*/true); if (dso) - return dso; + goto out_unlock; file_name = vdso__get_compat_file(vdso_file); if (!file_name) - return NULL; + goto out_unlock; - return __machine__addnew_vdso(machine, vdso_file->dso_name, file_name); + dso = __machine__addnew_vdso(machine, vdso_file->dso_name, file_name); +out_unlock: + up_write(&machine->dsos.lock); + return dso; } static int __machine__findnew_vdso_compat(struct machine *machine, @@ -332,33 +341,38 @@ struct dso *machine__findnew_vdso(struct machine *machine, { struct vdso_info *vdso_info; struct dso *dso = NULL; - char *file; + const char *file; + dso = machine__find_vdso(machine, thread); + if (dso) + return dso; + + down_write(&machine->dsos.lock); if (!machine->vdso_info) machine->vdso_info = vdso_info__new(); vdso_info = machine->vdso_info; - if (!vdso_info) + if (!vdso_info) { + up_write(&machine->dsos.lock); return NULL; - - dso = machine__find_vdso(machine, thread); - if (dso) - return dso; + } #if BITS_PER_LONG == 64 + up_write(&machine->dsos.lock); if (__machine__findnew_vdso_compat(machine, thread, vdso_info, &dso)) return dso; + down_write(&machine->dsos.lock); #endif - dso = dsos__find(&machine->dsos, DSO__NAME_VDSO, true); - if (dso) - return dso; - - file = get_file(&vdso_info->vdso); - if (!file) - return NULL; + dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO, true, /*write_locked=*/true); + if (!dso) { + file = get_file(&vdso_info->vdso); + if (file) + dso = __machine__addnew_vdso(machine, DSO__NAME_VDSO, file); + } + up_write(&machine->dsos.lock); - return __machine__addnew_vdso(machine, DSO__NAME_VDSO, file); + return dso; } bool dso__is_vdso(struct dso *dso) -- 2.56.0.542.g3ef89b7020-goog