[tip: timers/urgent] time: Zero the upper 32-bits in __kernel_timespec on 32-bit

From: tip-bot2 for Dmitry Safonov
Date: Wed Nov 20 2019 - 19:23:30 EST

The following commit has been merged into the timers/urgent branch of tip:

Commit-ID: 7b8474466ed97be458c825f34a85f2c2b84c3f95
Gitweb: https://git.kernel.org/tip/7b8474466ed97be458c825f34a85f2c2b84c3f95
Author: Dmitry Safonov <dima@xxxxxxxxxx>
AuthorDate: Thu, 21 Nov 2019 00:03:03
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Thu, 21 Nov 2019 01:17:58 +01:00

time: Zero the upper 32-bits in __kernel_timespec on 32-bit

On compat interfaces, the high order bits of nanoseconds should be zeroed
out. This is because the application code or the libc do not guarantee
zeroing of these. If used without zeroing, kernel might be at risk of using
timespec values incorrectly.

Originally it was handled correctly, but lost during is_compat_syscall()
cleanup. Revert the condition back to check CONFIG_64BIT.

Fixes: 98f76206b335 ("compat: Cleanup in_compat_syscall() callers")
Reported-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20191121000303.126523-1-dima@xxxxxxxxxx
kernel/time/time.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/time/time.c b/kernel/time/time.c
index 5c54ca6..83f403e 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -881,7 +881,8 @@ int get_timespec64(struct timespec64 *ts,
ts->tv_sec = kts.tv_sec;

/* Zero out the padding for 32 bit systems or in compat mode */
- if (IS_ENABLED(CONFIG_64BIT_TIME) && in_compat_syscall())
+ in_compat_syscall()))
kts.tv_nsec &= 0xFFFFFFFFUL;

ts->tv_nsec = kts.tv_nsec;