IB/ucm: Fix Spectre v1 vulnerability
authorGustavo A. R. Silva <gustavo@embeddedor.com>
Tue, 16 Oct 2018 14:32:40 +0000 (16:32 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 10 Nov 2018 15:48:35 +0000 (07:48 -0800)
commitf0e3b74a4dc0ce27abccdfdcd41eae73cee4b9ac
treec852c9924765f5f8bb5fc328431a1dfb270af32a
parent66448066c2b1ec587e6168a9206ffedd11d94444
IB/ucm: Fix Spectre v1 vulnerability

commit 0295e39595e1146522f2722715dba7f7fba42217 upstream.

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/ucm.c:1127 ib_ucm_write() warn: potential
spectre issue 'ucm_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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/infiniband/core/ucm.c