m68k: q40: Fix info-leak in rtc_ioctl

When the option is RTC_PLL_GET, pll will be copied to userland
via copy_to_user. pll is initialized using mach_get_rtc_pll indirect
call and mach_get_rtc_pll is only assigned with function
q40_get_rtc_pll in arch/m68k/q40/config.c.
In function q40_get_rtc_pll, the field pll_ctrl is not initialized.
This will leak uninitialized stack content to userland.
Fix this by zeroing the uninitialized field.

Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
Link: https://lore.kernel.org/r/20190927121544.7650-1-huangfq.daxian@gmail.com
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

diff --git a/arch/m68k/q40/config.c b/arch/m68k/q40/config.c
index e63eb5f..f318900 100644 (file)
--- a/arch/m68k/q40/config.c
+++ b/arch/m68k/q40/config.c
@@ -264,6 +264,7 @@ static int q40_get_rtc_pll(struct rtc_pll_info *pll)
 {
        int tmp = Q40_RTC_CTRL;
 
+       pll->pll_ctrl = 0;
        pll->pll_value = tmp & Q40_RTC_PLL_MASK;
        if (tmp & Q40_RTC_PLL_SIGN)
                pll->pll_value = -pll->pll_value;