[PATCH v1 2/5] IB/uverbs: ex_query_device: check request's comp_mask

[Yann Droneaud <ydroneaud-RlY5vtjFyJ3QT0dZR+AlfA@public.gmane.org>]

This patch ensures the extended QUERY_DEVICE uverbs request's
comp_mask has only known and supported bits (currently none).

If userspace set unknown features bits, -EINVAL will be returned,
ensuring current programs are not allowed to set random feature
bits: such bits could enable new extended features in future kernel
versions and those features can trigger a behavior not unsupported
by the older programs or make the newer kernels return an error
for a request which was valid on older kernels.

Additionally, returning an error for unsupported feature would
allow userspace to probe/discover which extended features are
currently supported by a kernel.

Link: http://mid.gmane.org/cover.1422553023.git.ydroneaud-RlY5vtjFyJ3QT0dZR+AlfA@public.gmane.org
Cc: Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Cc: Shachar Raindel <raindel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Cc: Eli Cohen <eli-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Cc: Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Yann Droneaud <ydroneaud-RlY5vtjFyJ3QT0dZR+AlfA@public.gmane.org>
---
 drivers/infiniband/core/uverbs_cmd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index 6ef06a9b4362..fbcc54b86795 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -3312,6 +3312,9 @@ int ib_uverbs_ex_query_device(struct ib_uverbs_file *file,
 	if (err)
 		return err;
 
+	if (cmd.comp_mask)
+		return -EINVAL;
+
 	if (cmd.reserved)
 		return -EINVAL;
 
-- 
2.1.0

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