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switchtec: Fix Spectre v1 vulnerability 

p.port can is 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/pci/switch/switchtec.c:912 ioctl_port_to_pff() warn: potential spectre issue 'pcfg->dsp_pff_inst_id' [r]

Fix this by sanitizing p.port before using it to index
pcfg->dsp_pff_inst_id

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

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Logan Gunthorpe <logang@deltatee.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Gustavo A. R. Silva 2018-08-16 14:06:46 -05:00 committed by Bjorn Helgaas
parent 50ca031b51
commit 46feb6b495
1 changed files with 4 additions and 0 deletions
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4
drivers/pci/switch/switchtec.c
View File

@ -14,6 +14,8 @@
#include <linux/poll.h>
#include <linux/wait.h>
#include <linux/nospec.h>
MODULE_DESCRIPTION("Microsemi Switchtec(tm) PCIe Management Driver");
MODULE_VERSION("0.1");
MODULE_LICENSE("GPL");
@ -909,6 +911,8 @@ static int ioctl_port_to_pff(struct switchtec_dev *stdev,
default:
if (p.port > ARRAY_SIZE(pcfg->dsp_pff_inst_id))
return -EINVAL;
p.port = array_index_nospec(p.port,
ARRAY_SIZE(pcfg->dsp_pff_inst_id) + 1);
p.pff = ioread32(&pcfg->dsp_pff_inst_id[p.port - 1]);
break;
}