regset: Prevent null pointer reference on readonly regsets

commit c8e252586f8d5de906385d8cf6385fee289a825e upstream.

The regset common infrastructure assumed that regsets would always
have .get and .set methods, but not necessarily .active methods.
Unfortunately people have since written regsets without .set methods.

Rather than putting in stub functions everywhere, handle regsets with
null .get or .set methods explicitly.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@hack.frob.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 9ba2ac755a7..618493e44ae 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1422,7 +1422,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
         for (i = 1; i < view->n; ++i) {
                 const struct user_regset *regset = &view->regsets[i];
                 do_thread_regset_writeback(t->task, regset);
-                if (regset->core_note_type &&
+                if (regset->core_note_type && regset->get &&
                     (!regset->active || regset->active(t->task, regset))) {
                         int ret;
                         size_t size = regset->n * regset->size;