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Re: [PATCH v06 14/36] arm uapi asm/signal.h: include <stddef.h> for size_t in userspace

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On Wed, Aug 09, 2017 at 02:41:59PM +0200, Arnd Bergmann wrote:
> On Wed, Aug 9, 2017 at 12:57 AM, Dmitry V. Levin <ldv@altlinux.org> wrote:
> > On Sun, Aug 06, 2017 at 06:44:05PM +0200, Mikko Rapeli wrote:
> >> Arnd Bergmann <arnd@arndb.de> doubts that __kernel_size_t could be used here
> >> so trying to fall back to gcc's <stddef.h>.
> >
> > The only architecture where you cannot do this safely is x86 family
> > because of x32 exception.  If there is no chance that the change will
> > affect x32, feel free to replace size_t with __kernel_size_t like I did
> > some time ago, see
> > http://lkml.kernel.org/r/20170302002022.GB27097@altlinux.org
> 
> There is another problem: on some 32-bit architectures, size_t is
> defined as 'unsigned int', while '__kernel_size_t' is defined as 'unsigned
> long'. These obviously have the same size, but the man page
> explicitly defines it as 'size_t ss_size'.
> 
> If a user space program accesses the field in a way requires an
> exact type match, it gets a warning or error, e.g.
> 
> 1. printf("signal with %zd bytes\n", stack->ss_size);
> 2. size_t *pointer_to_size_t = &stack->ss_size;
> 3. assert(__builtin_types_compatible_p(size_t, typeof(stack->ss_size)))
> 
> Not sure how important those are, but I think there is at least a risk
> of any of those showing up in user space.

Agreed, one has to take this issue into consideration when replacing
size_t with __kernel_size_t.


-- 
ldv

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[PATCH v06 00/36] Userspace compile test and fixes for exported uapi header files Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:10 +0200
  [PATCH v06 16/36] uapi linux/dlm_netlink.h: include linux/dlmconstants.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:10 +0200
  [PATCH v06 34/36] uapi: break dependency loop between <linux/hdlc/ioctl.h> and <linux/if.h> Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:10 +0200
  [PATCH v06 12/36] x86 uapi asm/signal.h: use __kernel_size_t instead of size_t Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:10 +0200
    Re: [PATCH v06 12/36] x86 uapi asm/signal.h: use __kernel_size_t  instead of size_t Arnd Bergmann <arnd@arndb.de> - 2017-08-07 16:40 +0200
    Re: [PATCH v06 12/36] x86 uapi asm/signal.h: use __kernel_size_t  instead of size_t "Dmitry V. Levin" <ldv@altlinux.org> - 2017-08-09 01:00 +0200
  [PATCH v06 22/36] uapi linux/reiserfs_xattr.h: use __kernel_size_t instead of size_t Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:10 +0200
    Re: [PATCH v06 22/36] uapi linux/reiserfs_xattr.h: use  __kernel_size_t instead of size_t "Dmitry V. Levin" <ldv@altlinux.org> - 2017-08-09 01:20 +0200
      Re: [PATCH v06 05/36] uapi linux/sysctl.h: use __kernel_size_t  instead of size_t Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-09 09:30 +0200
  [PATCH v06 14/36] arm uapi asm/signal.h: include <stddef.h> for size_t in userspace Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:20 +0200
    Re: [PATCH v06 14/36] arm uapi asm/signal.h: include <stddef.h> for  size_t in userspace "Dmitry V. Levin" <ldv@altlinux.org> - 2017-08-09 01:00 +0200
      Re: [PATCH v06 14/36] arm uapi asm/signal.h: include <stddef.h> for  size_t in userspace Arnd Bergmann <arnd@arndb.de> - 2017-08-09 14:50 +0200
        Re: [PATCH v06 14/36] arm uapi asm/signal.h: include <stddef.h> for  size_t in userspace "Dmitry V. Levin" <ldv@altlinux.org> - 2017-08-09 15:00 +0200
  [PATCH v06 33/36] uapi linux/fsmap.h: use __kernel_size_t instead of size_t Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:20 +0200
    Re: [PATCH v06 33/36] uapi linux/fsmap.h: use __kernel_size_t  instead of size_t "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-07 18:00 +0200
      Re: [PATCH v06 33/36] uapi linux/fsmap.h: use __kernel_size_t instead  of size_t Arnd Bergmann <arnd@arndb.de> - 2017-08-07 18:10 +0200
        Re: [PATCH v06 33/36] uapi linux/fsmap.h: use __kernel_size_t  instead of size_t "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-07 18:50 +0200
          Re: [PATCH v06 33/36] uapi linux/fsmap.h: use __kernel_size_t instead  of size_t Arnd Bergmann <arnd@arndb.de> - 2017-08-07 22:30 +0200
            Re: [PATCH v06 33/36] uapi linux/fsmap.h: use __kernel_size_t  instead of size_t "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-09 01:10 +0200
              Re: [PATCH v06 33/36] uapi linux/fsmap.h: use __kernel_size_t instead  of size_t Arnd Bergmann <arnd@arndb.de> - 2017-08-09 10:30 +0200
  [PATCH v06 01/36] Add scripts/headers_compile_test.sh: compile test for exported uapi headers Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:20 +0200
  [PATCH v06 20/36] uapi linux/scc.h: include linux/sockios.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:20 +0200
  [PATCH v06 18/36] uapi linux/errqueue.h: include linux/time.h in user space Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
    Re: [PATCH v06 18/36] uapi linux/errqueue.h: include linux/time.h in  user space Willem de Bruijn <willemdebruijn.kernel@gmail.com> - 2017-08-06 22:30 +0200
      Re: [PATCH v06 18/36] uapi linux/errqueue.h: include linux/time.h in  user space Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 23:00 +0200
    Re: [PATCH v06 18/36] uapi linux/errqueue.h: include linux/time.h in  user space Willem de Bruijn <willemdebruijn.kernel@gmail.com> - 2017-08-06 22:30 +0200
      Re: [PATCH v06 18/36] uapi linux/errqueue.h: include linux/time.h in  user space Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 23:00 +0200
        Re: [PATCH v06 18/36] uapi linux/errqueue.h: include linux/time.h in  user space Willem de Bruijn <willemdebruijn.kernel@gmail.com> - 2017-08-06 23:30 +0200
          Re: [PATCH v06 18/36] uapi linux/errqueue.h: include linux/time.h in  user space Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 23:40 +0200
            Re: [PATCH v06 18/36] uapi linux/errqueue.h: include linux/time.h in  user space Willem de Bruijn <willemdebruijn.kernel@gmail.com> - 2017-08-06 23:50 +0200
              Re: [PATCH v06 18/36] uapi linux/errqueue.h: include linux/time.h in  user space Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-07 00:00 +0200
                Re: [PATCH v06 18/36] uapi linux/errqueue.h: include linux/time.h in  user space Willem de Bruijn <willemdebruijn.kernel@gmail.com> - 2017-08-07 00:10 +0200
  [PATCH v06 36/36] uapi linux/kfd_ioctl.h: use __u32 and __u64 instead of uint32_t and uint64_t Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
    Re: [PATCH v06 36/36] uapi linux/kfd_ioctl.h: use __u32 and __u64  instead of uint32_t and uint64_t Arnd Bergmann <arnd@arndb.de> - 2017-08-07 17:10 +0200
  [PATCH v06 06/36] uapi asm-generic/ipcbuf.h: include linux/posix_types.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
  [PATCH v06 17/36] uapi linux/sctp.h: use __u8, __u16 and __u32 from linux/types.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
  [PATCH v06 07/36] uapi asm-generic/msgbuf.h: include asm/ipcbuf.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
  [PATCH v06 25/36] uapi linux/android/binder.h: use __kernel_pid_t and __kernel_uid_t Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
  [PATCH v06 02/36] uapi scsi/scsi_bsg_fc.h: use __u8, __u32 and __u64 from linux/types.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
  [PATCH v06 11/36] uapi asm-generic/ucontext.h: include asm/signal.h and asm/sigcontext.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
  [PATCH v06 10/36] uapi asm-generic/signal.h: use __kernel_size_t instead of size_t Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
  [PATCH v06 24/36] uapi linux/coda_psdev.h: move upc_req definition from uapi to kernel side headers Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
  [PATCH v06 09/36] uapi asm-generic/sembuf.h: include asm/posix_types.h and asm/ipcbuf.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
    Re: [PATCH v06 09/36] uapi asm-generic/sembuf.h: include  asm/posix_types.h and asm/ipcbuf.h "Dmitry V. Levin" <ldv@altlinux.org> - 2017-08-09 00:50 +0200
  [PATCH v06 27/36] uapi xen/gntdev.h: include xen/privcmd.h and define grant_ref_t Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
  [PATCH v06 30/36] uapi rdma/rdma_user_rxe.h: include in.h and in6.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
    Re: [PATCH v06 30/36] uapi rdma/rdma_user_rxe.h: include in.h and  in6.h Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-08-09 01:20 +0200
      Re: [PATCH v06 30/36] uapi rdma/rdma_user_rxe.h: include in.h and in6.h Moni Shoua <monis@mellanox.com> - 2017-08-09 15:50 +0200
        Re: [PATCH v06 30/36] uapi rdma/rdma_user_rxe.h: include in.h and  in6.h Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-08-09 18:00 +0200
          Re: [PATCH v06 30/36] uapi rdma/rdma_user_rxe.h: include in.h and  in6.h "Dmitry V. Levin" <ldv@altlinux.org> - 2017-08-10 04:50 +0200
            Re: [PATCH v06 30/36] uapi rdma/rdma_user_rxe.h: include in.h and  in6.h Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-08-10 18:20 +0200
  [PATCH v06 13/36] x86 uapi asm/sembuf.h: include linux/types.h and linux/ipc.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
    Re: [PATCH v06 13/36] x86 uapi asm/sembuf.h: include linux/types.h  and linux/ipc.h "Dmitry V. Levin" <ldv@altlinux.org> - 2017-08-09 01:00 +0200
  [PATCH v06 26/36] uapi xen/privcmd.h: fix compilation in userspace Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200
  [PATCH v06 28/36] uapi xen/evtchn.h: include xen/privcmd.h Mikko Rapeli <mikko.rapeli@iki.fi> - 2017-08-06 19:30 +0200

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