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Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handl
From: |
Paul Burton |
Subject: |
Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling |
Date: |
Tue, 24 Jun 2014 00:10:10 +0100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Mon, Jun 23, 2014 at 11:42:14PM +0100, Peter Maydell wrote:
> On 23 June 2014 23:36, Paul Burton <address@hidden> wrote:
> > Actually no, I don't think you're right about that afterall. The
> > argument union itself is never modified. I imagine if it were then it
> > would be painful in the case of the semctl syscall where the union is
> > passed directly as an argument, rather than as a pointer as it is for
> > the ipc syscall.
> >
> > What may be modified is the data pointed to by the pointers within union
> > semun. That is already handled by do_semctl & the translate functions it
> > calls.
>
> Except if you look at do_semctl you see code like:
> case GETVAL:
> case SETVAL:
> arg.val = tswap32(target_su.val);
> ret = get_errno(semctl(semid, semnum, cmd, arg));
> target_su.val = tswap32(arg.val);
> break;
>
> which clearly is just modifying fields in the target_semun union.
> So something's wrong (probably that code)...
Yes, both Linux & man semctl agree that GETVAL returns the value of
the semaphore as the return value of the syscall. So I believe the
assignment to target_su.val there is (functionally harmless) garbage.
Thanks,
Paul
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- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, (continued)
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, Peter Maydell, 2014/06/23
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, Paul Burton, 2014/06/23
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, Peter Maydell, 2014/06/23
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, Paul Burton, 2014/06/23
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, Peter Maydell, 2014/06/23
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, Paul Burton, 2014/06/23
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, Peter Maydell, 2014/06/24
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, Paul Burton, 2014/06/24
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, Paul Burton, 2014/06/23
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling, Peter Maydell, 2014/06/23
- Re: [Qemu-devel] [PATCH] linux-user: fix ipc(SEMCTL, ...) argument handling,
Paul Burton <=