4.14-stable review patch. If anyone has any objections, please let me know.
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From: Gustavo A. R. Silva gustavo@embeddedor.com
commit 46feb6b495f7628a6dbf36c4e6d80faf378372d4 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/pci/switch/switchtec.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/pci/switch/switchtec.c +++ b/drivers/pci/switch/switchtec.c @@ -24,6 +24,8 @@ #include <linux/cdev.h> #include <linux/wait.h>
+#include <linux/nospec.h> + MODULE_DESCRIPTION("Microsemi Switchtec(tm) PCIe Management Driver"); MODULE_VERSION("0.1"); MODULE_LICENSE("GPL"); @@ -1173,6 +1175,8 @@ static int ioctl_port_to_pff(struct swit 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; }