On Mon, 15 Apr 2019 21:35:17 +0200, Gustavo A. R. Silva wrote:

Hi all,

Friendly ping:

Who can take this?

All platforms that support ISA boards are so old and they don't suffer from Spectre at all.

thanks,

Takashi

Thanks

Gustavo

On 3/26/19 1:32 PM, Gustavo A. R. Silva wrote:

...

header->number and i are 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:

sound/isa/wavefront/wavefront_synth.c:792 wavefront_send_patch() warn: potential spectre issue 'dev->patch_status' [w] (local cap) sound/isa/wavefront/wavefront_synth.c:819 wavefront_send_program() warn: potential spectre issue 'dev->prog_status' [w] (local cap) sound/isa/wavefront/wavefront_synth.c:1197 wavefront_send_alias() warn: potential spectre issue 'dev->sample_status' [w] sound/isa/wavefront/wavefront_synth.c:1248 wavefront_send_multisample() warn: potential spectre issue 'dev->sample_status' [w] sound/isa/wavefront/wavefront_synth.c:1548 wavefront_synth_control() warn: potential spectre issue 'dev->sample_status' [r] (local cap)

Fix this by sanitizing header->number and i before using them to index dev->patch_status, dev->prog_status, dev->sample_status.

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://lore.kernel.org/lkml/20180423164740.GY17484@dhcp22.suse.cz/

Cc: stable@vger.kernel.org Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com

---

sound/isa/wavefront/wavefront_synth.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)

diff --git a/sound/isa/wavefront/wavefront_synth.c b/sound/isa/wavefront/wavefront_synth.c index 0b1e4b34b299..a78e125dfdf9 100644 --- a/sound/isa/wavefront/wavefront_synth.c +++ b/sound/isa/wavefront/wavefront_synth.c @@ -31,6 +31,7 @@ #include <linux/moduleparam.h> #include <linux/slab.h> #include <linux/module.h> +#include <linux/nospec.h> #include <sound/core.h> #include <sound/snd_wavefront.h> #include <sound/initval.h> @@ -788,6 +789,8 @@ wavefront_send_patch (snd_wavefront_t *dev, wavefront_patch_info *header)

if (header->number >= ARRAY_SIZE(dev->patch_status)) return -EINVAL;

• header->number = array_index_nospec(header->number,

• 			    ARRAY_SIZE(dev->patch_status));
  
  

  dev->patch_status[header->number] |= WF_SLOT_FILLED;

@@ -815,6 +818,8 @@ wavefront_send_program (snd_wavefront_t *dev, wavefront_patch_info *header)

if (header->number >= ARRAY_SIZE(dev->prog_status)) return -EINVAL;

• header->number = array_index_nospec(header->number,

• 			    ARRAY_SIZE(dev->prog_status));
  
  

  dev->prog_status[header->number] = WF_SLOT_USED;

@@ -1194,6 +1199,11 @@ wavefront_send_alias (snd_wavefront_t *dev, wavefront_patch_info *header) return -EIO; }

• if (header->number >= ARRAY_SIZE(dev->sample_status))

• return -EINVAL;
  

• header->number = array_index_nospec(header->number,

• 			    ARRAY_SIZE(dev->sample_status));
  

• dev->sample_status[header->number] = (WF_SLOT_FILLED|WF_ST_ALIAS);

  return (0);

@@ -1245,6 +1255,12 @@ wavefront_send_multisample (snd_wavefront_t *dev, wavefront_patch_info *header) return -EIO; }

• if (header->number >= ARRAY_SIZE(dev->sample_status)) {

• kfree(msample_hdr);
  

• return -EINVAL;
  

• }

• header->number = array_index_nospec(header->number,

• 			    ARRAY_SIZE(dev->sample_status));
  

  dev->sample_status[header->number] = (WF_SLOT_FILLED|WF_ST_MULTISAMPLE);

  kfree(msample_hdr);

@@ -1545,6 +1561,7 @@ wavefront_synth_control (snd_wavefront_card_t *acard, wc->status = EINVAL; return -EINVAL; }

• i = array_index_nospec(i, WF_MAX_SAMPLE);
  

  wc->rbuf[0] = dev->sample_status[i]; wc->status = 0; return 0;