header->number 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:

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 before using it to index dev->patch_status, dev->prog_status and 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://marc.info/?l=linux-kernel&m=152449131114778&w=2

Cc: stable@vger.kernel.org Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com --- sound/isa/wavefront/wavefront_synth.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/sound/isa/wavefront/wavefront_synth.c b/sound/isa/wavefront/wavefront_synth.c index 0b1e4b34b299..80196a533a36 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> @@ -788,7 +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;

bptr = buf; @@ -815,7 +817,8 @@ 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;

/* XXX need to zero existing SLOT_USED bit for program_status[i] @@ -1194,6 +1197,10 @@ 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 +1252,10 @@ wavefront_send_multisample (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_MULTISAMPLE);

kfree(msample_hdr); @@ -1539,12 +1550,13 @@ wavefront_synth_control (snd_wavefront_card_t *acard,

case WFC_IDENTIFY_SLOT_TYPE: i = wc->wbuf[0] | (wc->wbuf[1] << 7); - if (i <0 || i >= WF_MAX_SAMPLE) { + if (i < 0 || i >= WF_MAX_SAMPLE) { snd_printk ("invalid slot ID %d\n", i); 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;