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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 1ed37ba72343f2f62990a32cd95e586d8c0b02a9..a64fde6c626ebdf117638a06bec8710bb7e0f714 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1452,7 +1452,7 @@ 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;

diff --git a/include/linux/regset.h b/include/linux/regset.h
index 8abee65562230fe05174d2ded6bc8ec50249348b..5150fd16ef93cbb38a840fb6667b56b937697f51 100644 (file)
--- a/include/linux/regset.h
+++ b/include/linux/regset.h
@@ -335,6 +335,9 @@ static inline int copy_regset_to_user(struct task_struct *target,
 {
        const struct user_regset *regset = &view->regsets[setno];
 
+       if (!regset->get)
+               return -EOPNOTSUPP;
+
        if (!access_ok(VERIFY_WRITE, data, size))
                return -EIO;
 
@@ -358,6 +361,9 @@ static inline int copy_regset_from_user(struct task_struct *target,
 {
        const struct user_regset *regset = &view->regsets[setno];
 
+       if (!regset->set)
+               return -EOPNOTSUPP;
+
        if (!access_ok(VERIFY_READ, data, size))
                return -EIO;