3.16.65-rc1 review patch. If anyone has any objections, please let me know.
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From: "Gustavo A. R. Silva" gustavo@embeddedor.com
commit 4aea96f4237cea0c51a8bc87c0db31f0f932f1f0 upstream.
info.mode and info.port are indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability.
These issues were detected with the help of Smatch:
sound/synth/emux/emux_hwdep.c:72 snd_emux_hwdep_misc_mode() warn: potential spectre issue 'emu->portptrs[i]->ctrls' [w] (local cap) sound/synth/emux/emux_hwdep.c:75 snd_emux_hwdep_misc_mode() warn: potential spectre issue 'emu->portptrs' [w] (local cap) sound/synth/emux/emux_hwdep.c:75 snd_emux_hwdep_misc_mode() warn: potential spectre issue 'emu->portptrs[info.port]->ctrls' [w] (local cap)
Fix this by sanitizing both info.mode and info.port before using them to index emu->portptrs[i]->ctrls, emu->portptrs[info.port]->ctrls and emu->portptrs.
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: Takashi Iwai tiwai@suse.de [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- sound/synth/emux/emux_hwdep.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/sound/synth/emux/emux_hwdep.c +++ b/sound/synth/emux/emux_hwdep.c @@ -22,9 +22,9 @@ #include <sound/core.h> #include <sound/hwdep.h> #include <asm/uaccess.h> +#include <linux/nospec.h> #include "emux_voice.h"
- #define TMP_CLIENT_ID 0x1001
/* @@ -66,13 +66,16 @@ snd_emux_hwdep_misc_mode(struct snd_emux return -EFAULT; if (info.mode < 0 || info.mode >= EMUX_MD_END) return -EINVAL; + info.mode = array_index_nospec(info.mode, EMUX_MD_END);
if (info.port < 0) { for (i = 0; i < emu->num_ports; i++) emu->portptrs[i]->ctrls[info.mode] = info.value; } else { - if (info.port < emu->num_ports) + if (info.port < emu->num_ports) { + info.port = array_index_nospec(info.port, emu->num_ports); emu->portptrs[info.port]->ctrls[info.mode] = info.value; + } } return 0; }