futex: Adjust absolute futex timeouts with per time namespace offset

For all commands except FUTEX_WAIT, the timeout is interpreted as an
absolute value. This absolute value is inside the task's time namespace and
has to be converted to the host's time.

Fixes: 5a590f35add9 ("posix-clocks: Wire up clock_gettime() with timens offsets")
Reported-by: Hans van der Laan <j.h.vanderlaan@student.utwente.nl>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201015160020.293748-1-avagin@gmail.com

diff --git a/kernel/futex.c b/kernel/futex.c
index 680854dcf1561f918dbcbc8d99a8187a146685a4..be68ac0d49adf6cf2eeff7c9c3514dc03ffcb5a9 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -39,6 +39,7 @@
 #include <linux/freezer.h>
 #include <linux/memblock.h>
 #include <linux/fault-inject.h>
+#include <linux/time_namespace.h>
 
 #include <asm/futex.h>
 
@@ -3797,6 +3798,8 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
                t = timespec64_to_ktime(ts);
                if (cmd == FUTEX_WAIT)
                        t = ktime_add_safe(ktime_get(), t);
+               else if (!(op & FUTEX_CLOCK_REALTIME))
+                       t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
                tp = &t;
        }
        /*
@@ -3989,6 +3992,8 @@ SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val,
                t = timespec64_to_ktime(ts);
                if (cmd == FUTEX_WAIT)
                        t = ktime_add_safe(ktime_get(), t);
+               else if (!(op & FUTEX_CLOCK_REALTIME))
+                       t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
                tp = &t;
        }
        if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||