[PATCH AUTOSEL 5.4 016/330] m68k: q40: Fix info-leak in rtc_ioctl

[Sasha Levin]

From: Fuqian Huang <huangfq.daxian@xxxxxxxxx>

[ Upstream commit 7cf78b6b12fd5550545e4b73b35dca18bd46b44c ]

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@xxxxxxxxx>
Link: https://lore.kernel.org/r/20190927121544.7650-1-huangfq.daxian@xxxxxxxxx
Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/m68k/q40/config.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/m68k/q40/config.c b/arch/m68k/q40/config.c
index e63eb5f069995..f31890078197e 100644
--- 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;
-- 
2.25.1