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Subject[patch 07/40] IB/uverbs: Fix checking of userspace object ownership

-stable review patch. If anyone has any objections, please let us know.

------------------
From: Roland Dreier <rolandd@cisco.com>
Upstream as cbfb50e6e2e9c580848c0f51d37c24cdfb1cb704

Commit 9ead190b ("IB/uverbs: Don't serialize with ib_uverbs_idr_mutex")
rewrote how userspace objects are looked up in the uverbs module's
idrs, and introduced a severe bug in the process: there is no checking
that an operation is being performed by the right process any more.
Fix this by adding the missing check of uobj->context in __idr_get_uobj().

Apparently everyone is being very careful to only touch their own
objects, because this bug was introduced in June 2006 in 2.6.18, and
has gone undetected until now.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/infiniband/core/uverbs_cmd.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -147,8 +147,12 @@ static struct ib_uobject *__idr_get_uobj

spin_lock(&ib_uverbs_idr_lock);
uobj = idr_find(idr, id);
- if (uobj)
- kref_get(&uobj->ref);
+ if (uobj) {
+ if (uobj->context == context)
+ kref_get(&uobj->ref);
+ else
+ uobj = NULL;
+ }
spin_unlock(&ib_uverbs_idr_lock);

return uobj;
--
-
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