From: H. Peter Anvin <hpa@zytor.com>
Date: Fri, 2 Mar 2012 18:43:48 +0000 (-0800)
Subject: regset: Prevent null pointer reference on readonly regsets
X-Git-Tag: v3.2.10~78
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=58458d037c19e6d3ae5bd7cdfafc423d0d2d7984

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>
---

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 21ac5ee4b43f..6ff96c68a2a0 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1421,7 +1421,7 @@ 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 8abee6556223..5150fd16ef93 100644
--- 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;