[PATCH 5.9 355/391] futex: Adjust absolute futex timeouts with per time namespace offset

[Greg Kroah-Hartman]

From: Andrei Vagin <ava...@gmail.com>

commit c2f7d08cccf4af2ce6992feaabb9e68e4ae0bff3 upstream.

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.vanderl...@student.utwente.nl>
Signed-off-by: Andrei Vagin <ava...@gmail.com>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Reviewed-by: Dmitry Safonov <0x7f454...@gmail.com>
Cc: <sta...@vger.kernel.org>
Link: https://lore.kernel.org/r/20201015160020.293748-1-ava...@gmail.com
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 kernel/futex.c |    5 +++++
 1 file changed, 5 insertions(+)

--- 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>
 
@@ -3799,6 +3800,8 @@ SYSCALL_DEFINE6(futex, u32 __user *, uad
                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;
        }
        /*
@@ -3991,6 +3994,8 @@ SYSCALL_DEFINE6(futex_time32, u32 __user
                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 ||