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Subject[PATCH] compat: Fix endian issue in union sigval
In 64bit architecture, sigval_int is the high 32bit of sigval_ptr in
big endian kernel compare with low 32bit of sigval_ptr in little
endian kernel. reference:

typedef union sigval {
int sival_int;
void *sival_ptr;
} sigval_t;

During compat_mq_notify or compat_timer_create, kernel get sigval
from user space by reading sigval.sival_int. This is correct in 32 bit
kernel and in 64bit little endian kernel. And It is wrong in 64bit big
endian kernel:
It get the high 32bit of sigval_ptr and put it to low 32bit of
sigval_ptr. And the high 32bit sigval_ptr in empty in arm 32bit user
space struct. So, kernel lost the value of sigval_ptr.

The following patch get the sigval_ptr in stead of sigval_int in order
to avoid endian issue.
Test pass in arm64 big endian and little endian kernel.

Signed-off-by: Zhang Jian(Bamvor) <>
ipc/compat_mq.c | 7 ++-----
kernel/compat.c | 6 ++----
2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/ipc/compat_mq.c b/ipc/compat_mq.c
index ef6f91c..2e07343 100644
--- a/ipc/compat_mq.c
+++ b/ipc/compat_mq.c
@@ -99,11 +99,8 @@ COMPAT_SYSCALL_DEFINE2(mq_notify, mqd_t, mqdes,
if (u_notification) {
struct sigevent n;
p = compat_alloc_user_space(sizeof(*p));
- if (get_compat_sigevent(&n, u_notification))
- return -EFAULT;
- if (n.sigev_notify == SIGEV_THREAD)
- n.sigev_value.sival_ptr = compat_ptr(n.sigev_value.sival_int);
- if (copy_to_user(p, &n, sizeof(*p)))
+ if (get_compat_sigevent(&n, u_notification) ||
+ copy_to_user(p, &n, sizeof(*p)))
return -EFAULT;
return sys_mq_notify(mqdes, p);
diff --git a/kernel/compat.c b/kernel/compat.c
index ebb3c36..13a0e5d 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -871,16 +871,14 @@ COMPAT_SYSCALL_DEFINE4(clock_nanosleep, clockid_t, which_clock, int, flags,
* We currently only need the following fields from the sigevent
* structure: sigev_value, sigev_signo, sig_notify and (sometimes
* sigev_notify_thread_id). The others are handled in user mode.
- * We also assume that copying sigev_value.sival_int is sufficient
- * to keep all the bits of sigev_value.sival_ptr intact.
int get_compat_sigevent(struct sigevent *event,
const struct compat_sigevent __user *u_event)
memset(event, 0, sizeof(*event));
return (!access_ok(VERIFY_READ, u_event, sizeof(*u_event)) ||
- __get_user(event->sigev_value.sival_int,
- &u_event->sigev_value.sival_int) ||
+ __get_user(*(long long*)event->sigev_value.sival_ptr,
+ &u_event->sigev_value.sival_ptr) ||
__get_user(event->sigev_signo, &u_event->sigev_signo) ||
__get_user(event->sigev_notify, &u_event->sigev_notify) ||

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