commit 701956d401 upstream.
ipcnum 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/char/mwave/mwavedd.c:299 mwave_ioctl() warn: potential spectre issue 'pDrvData->IPCs' [w] (local cap)
Fix this by sanitizing ipcnum before using it to index pDrvData->IPCs.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
d3faea2d15