IB/uverbs: Safely extend existing attributes

Previously, we've used UVERBS_ATTR_SPEC_F_MIN_SZ for extending existing
attributes. The behavior of this flag was the kernel accepts anything
bigger than the minimum size it specified. This is unsafe, since in
order to safely extend an attribute, we need to make sure unknown size
is zeroed. Replacing UVERBS_ATTR_SPEC_F_MIN_SZ with
UVERBS_ATTR_SPEC_F_MIN_SZ_OR_ZERO, which essentially checks that the
unknown size is zero. In addition, attributes are now decorated with
UVERBS_ATTR_TYPE and UVERBS_ATTR_STRUCT, so we can provide the minimum
and known length.

Users of this flag needs to use copy_from_or_zero functions/macros.

Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

1 files changed, 9 insertions, 4 deletions

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 2357f2b29610..e9288d0f627e 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -2446,11 +2446,9 @@ static inline int ib_copy_to_udata(struct ib_udata *udata, void *src, size_t len
 	return copy_to_user(udata->outbuf, src, len) ? -EFAULT : 0;
 }
 
-static inline bool ib_is_udata_cleared(struct ib_udata *udata,
-				       size_t offset,
-				       size_t len)
+static inline bool ib_is_buffer_cleared(const void __user *p,
+					size_t len)
 {
-	const void __user *p = udata->inbuf + offset;
 	bool ret;
 	u8 *buf;
 
@@ -2466,6 +2464,13 @@ static inline bool ib_is_udata_cleared(struct ib_udata *udata,
 	return ret;
 }
 
+static inline bool ib_is_udata_cleared(struct ib_udata *udata,
+				       size_t offset,
+				       size_t len)
+{
+	return ib_is_buffer_cleared(udata->inbuf + offset, len);
+}
+
 /**
  * ib_modify_qp_is_ok - Check that the supplied attribute mask
  * contains all required attributes and no attributes not allowed for