commit a3671a4f973ee9d9621d60166cc3b037c397d604
author Gustavo A. R. Silva <gustavo@embeddedor.com> Tue Oct 16 16:59:01 2018 +0200
committer Doug Ledford <dledford@redhat.com> Tue Oct 16 12:47:40 2018 -0400
tree ef3c0975d7284a25fd265d63793c5edcee2d322f
parent 0295e39595e1146522f2722715dba7f7fba42217

RDMA/ucma: Fix Spectre v1 vulnerability

hdr.cmd can be indirectly controlled by user-space, hence leading to
a potential exploitation of the Spectre variant 1 vulnerability.

This issue was detected with the help of Smatch:

drivers/infiniband/core/ucma.c:1686 ucma_write() warn: potential
spectre issue 'ucma_cmd_table' [r] (local cap)

Fix this by sanitizing hdr.cmd before using it to index
ucm_cmd_table.

Notice that given that speculation windows are large, the policy is
to kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].

[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2

Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>