[PATCH 3.12 067/182] IB/nes: Return an error on ib_copy_from_udata() failure instead of NULL

Jiri Slaby
2014-05-13T09:38:24Z

From: Yann Droneaud <ydroneaud@opteya.com>

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

===============

commit 9d194d1025f463392feafa26ff8c2d8247f71be1 upstream.

In case of error while accessing to userspace memory, function
nes_create_qp() returns NULL instead of an error code wrapped through
ERR_PTR(). But NULL is not expected by ib_uverbs_create_qp(), as it
check for error with IS_ERR().

As page 0 is likely not mapped, it is going to trigger an Oops when
the kernel will try to dereference NULL pointer to access to struct
ib_qp's fields.

In some rare cases, page 0 could be mapped by userspace, which could
turn this bug to a vulnerability that could be exploited: the function
pointers in struct ib_device will be under userspace total control.

This was caught when using spatch (aka. coccinelle)
to rewrite calls to ib_copy_{from,to}_udata().

Link: https://www.gitorious.org/opteya/ib-hw-nes-create-qp-null
Link: https://www.gitorious.org/opteya/coccib/source/75ebf2c1033c64c1d81df13e4ae44ee99c989eba:ib_copy_udata.cocci
Link: http://marc.info/?i=cover.1394485254.git.ydroneaud@opteya.com
Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
drivers/infiniband/hw/nes/nes_verbs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/nes/nes_verbs.c b/drivers/infiniband/hw/nes/nes_verbs.c
index 5b53ca5a2284..09999cdec3b1 100644
--- a/drivers/infiniband/hw/nes/nes_verbs.c
+++ b/drivers/infiniband/hw/nes/nes_verbs.c
@@ -1186,7 +1186,7 @@ static struct ib_qp *nes_create_qp(struct ib_pd *ibpd,
nes_free_resource(nesadapter, nesadapter->allocated_qps, qp_num);
kfree(nesqp->allocated_buffer);
nes_debug(NES_DBG_QP, "ib_copy_from_udata() Failed \n");
- return NULL;
+ return ERR_PTR(-EFAULT);
}
if (req.user_wqe_buffers) {
virt_wqs = 1;
--
1.9.3