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Re: [Qemu-devel] [PATCH 02/12] linux-user: Dereference Pointer Argument
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH 02/12] linux-user: Dereference Pointer Argument to ipc/semctl Sys Call |
Date: |
Mon, 4 Aug 2014 18:04:10 +0100 |
On 4 August 2014 17:45, Tom Musta <address@hidden> wrote:
> When the ipc system call is used to wrap a semctl system call,
> the ptr argument to ipc needs to be dereferenced prior to passing
> it to the semctl handler. This is because the fourth argument to
> semctl is a union and not a pointer to a union.
>
> Signed-off-by: Tom Musta <address@hidden>
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 540001c..229c482 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -3135,9 +3135,15 @@ static abi_long do_ipc(unsigned int call, int first,
> ret = get_errno(semget(first, second, third));
> break;
>
> - case IPCOP_semctl:
> - ret = do_semctl(first, second, third, (union
> target_semun)(abi_ulong) ptr);
> + case IPCOP_semctl: {
> + /* The semun argument to semctl is passed by value, so dereference
> the
> + * ptr argument. */
> + abi_ulong atptr;
> + get_user_ual(atptr, (abi_ulong)ptr);
> + ret = do_semctl(first, second, third,
> + (union target_semun)(abi_ulong) atptr);
My review comments on this patch from Paul Burton:
http://patchwork.ozlabs.org/patch/363201/
apply here too: the change here to use get_user_ual()
looks plausible, except that do_semctl() writes to the
target_su in some cases, so how is this supposed to
pass the value back to the caller? Probably do_semctl()
is buggy, but the whole thing needs to be scrutinized
and fixed, not just this little corner...
thanks
-- PMM
- [Qemu-devel] [PATCH 00/12] target-ppc: Linux-User Mode Bug Fixes for Power, Tom Musta, 2014/08/04
- [Qemu-devel] [PATCH 01/12] linux-user: PPC64 semid_ds Doesnt Include _unused1 and _unused2, Tom Musta, 2014/08/04
- [Qemu-devel] [PATCH 02/12] linux-user: Dereference Pointer Argument to ipc/semctl Sys Call, Tom Musta, 2014/08/04
- Re: [Qemu-devel] [PATCH 02/12] linux-user: Dereference Pointer Argument to ipc/semctl Sys Call,
Peter Maydell <=
- [Qemu-devel] [PATCH 03/12] linux-user: Properly Handle semun Structure In Cross-Endian Situations, Tom Musta, 2014/08/04
- [Qemu-devel] [PATCH 04/12] linux-user: Make ipc syscall's third argument an abi_long, Tom Musta, 2014/08/04
- [Qemu-devel] [PATCH 05/12] linux-user: Conditionally Pass Attribute Pointer to mq_open(), Tom Musta, 2014/08/04
- [Qemu-devel] [PATCH 06/12] linux-user: Detect Negative Message Sizes in msgsnd System Call, Tom Musta, 2014/08/04
- [Qemu-devel] [PATCH 07/12] linux-user: Handle NULL argument to sched_{get, set}param, Tom Musta, 2014/08/04