On 2015/2/14 19:22, Catalin Marinas wrote: > On Fri, Feb 13, 2015 at 04:56:29PM -0500, Chris Metcalf wrote: >> On 2/13/2015 5:44 AM, Catalin Marinas wrote: >>> On Fri, Feb 13, 2015 at 04:00:43PM +0800, Bamvor Jian Zhang wrote: >>>> diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c >>>> index e299de396e9b..32601939a3c8 100644 >>>> --- a/arch/arm64/kernel/signal32.c >>>> +++ b/arch/arm64/kernel/signal32.c >>>> @@ -154,8 +154,7 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from) >>>> case __SI_TIMER: >>>> err |= __put_user(from->si_tid, &to->si_tid); >>>> err |= __put_user(from->si_overrun, &to->si_overrun); >>>> - err |= __put_user((compat_uptr_t)(unsigned long)from->si_ptr, >>>> - &to->si_ptr); >>>> + err |= __put_user(from->si_int, &to->si_int); >>>> break; >>>> case __SI_POLL: >>>> err |= __put_user(from->si_band, &to->si_band); >>>> @@ -184,7 +183,7 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from) >>>> case __SI_MESGQ: /* But this is */ >>>> err |= __put_user(from->si_pid, &to->si_pid); >>>> err |= __put_user(from->si_uid, &to->si_uid); >>>> - err |= __put_user((compat_uptr_t)(unsigned long)from->si_ptr, &to->si_ptr); >>>> + err |= __put_user(from->si_int, &to->si_int); >>>> break; >>>> case __SI_SYS: >>>> err |= __put_user((compat_uptr_t)(unsigned long) >> >> I must be confused here, but I don't see that these do anything different. >> >> If we are writing 32 bits to to->si_ptr or to->si_int, either way the high 32 bits >> are irrelevant. So whether we read it from from->si_ptr and massage the high bits, >> or just read it from from->si_int as a straight-up 32-bit quantity, either way it >> seems we should end up writing the same bits to userspace. >> >> I would understand the argument if we were overlaying the si_ptr/si_int union >> from a kernel-side siginfo_t where si_ptr and si_int are different sizes >> onto userspace, but it doesn't seem we ever do that. > > That's the problem, "from" above is a kernel siginfo_t while "to" is a > compat_siginfo_t. The call paths go something like: > > 1. user populates sival_int compat_sigevent and invokes > compat_sys_mq_notify() > 2. kernel get_compat_sigevent() copies compat_sigevent into the native > sigevent. compat and native sival_int are the same, no problem so > far. The other half of 64-bit sival_ptr is zeroed by a memset in this > function (this other half can be top or bottom, depending on > endianness) > 3. signal is about to be delivered to user via arch code. The > compat_ptr(from->si_ptr) conversion always takes the least > significant part of the native si_ptr. On big endian 64-bit, this is > zero because get_compat_sigevent() populated the top part of si_ptr > with si_int. > > So delivering such signals to compat user always sets si_int to 0. > Little endian is fine. > > A similar example is sys_timer_create() which takes a sigevent argument. > Maybe Bamvor has a test case. > A similar example is sys_timer_create() which takes a sigevent argument. > Maybe Bamvor has a test case. Yeap, this issue is came from glibc rt testcases(tst-cputimer1, tst-cputimer2, tst-cputimer3, tst-timer4, tst-timer5). The above test cases include timer_create syscall with sigevent.sigev_notify = SIGEV_THREAD. They failed when they compiled as armeb elf and run on aarch64_be kernel. When I try to fix it, I found sys_mq_notify is similar. regards bamvor > (btw, I'm off for a week, I'll follow up when I get back) > -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
