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regset: Prevent null pointer reference on readonly regsets
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>
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H. Peter Anvin authored and torvalds committed Mar 2, 2012
1 parent 1f033c1 commit c8e2525
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Showing 2 changed files with 7 additions and 1 deletion.
2 changes: 1 addition & 1 deletion fs/binfmt_elf.c
Expand Up @@ -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;
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6 changes: 6 additions & 0 deletions include/linux/regset.h
Expand Up @@ -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;

Expand All @@ -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;

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