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    Subject[PATCH 3.2 044/164] IB/core: don't disallow registering region starting at 0x0
    3.2.70-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Yann Droneaud <ydroneaud@opteya.com>

    commit 66578b0b2f69659f00b6169e6fe7377c4b100d18 upstream.

    In a call to ib_umem_get(), if address is 0x0 and size is
    already page aligned, check added in commit 8494057ab5e4
    ("IB/uverbs: Prevent integer overflow in ib_umem_get address
    arithmetic") will refuse to register a memory region that
    could otherwise be valid (provided vm.mmap_min_addr sysctl
    and mmap_low_allowed SELinux knobs allow userspace to map
    something at address 0x0).

    This patch allows back such registration: ib_umem_get()
    should probably don't care of the base address provided it
    can be pinned with get_user_pages().

    There's two possible overflows, in (addr + size) and in
    PAGE_ALIGN(addr + size), this patch keep ensuring none
    of them happen while allowing to pin memory at address
    0x0. Anyway, the case of size equal 0 is no more (partially)
    handled as 0-length memory region are disallowed by an
    earlier check.

    Link: http://mid.gmane.org/cover.1428929103.git.ydroneaud@opteya.com
    Cc: Shachar Raindel <raindel@mellanox.com>
    Cc: Jack Morgenstein <jackm@mellanox.com>
    Cc: Or Gerlitz <ogerlitz@mellanox.com>
    Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
    Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
    Reviewed-by: Haggai Eran <haggaie@mellanox.com>
    Signed-off-by: Doug Ledford <dledford@redhat.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/infiniband/core/umem.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/drivers/infiniband/core/umem.c
    +++ b/drivers/infiniband/core/umem.c
    @@ -101,8 +101,8 @@ struct ib_umem *ib_umem_get(struct ib_uc
    * If the combination of the addr and size requested for this memory
    * region causes an integer overflow, return error.
    */
    - if ((PAGE_ALIGN(addr + size) <= size) ||
    - (PAGE_ALIGN(addr + size) <= addr))
    + if (((addr + size) < addr) ||
    + PAGE_ALIGN(addr + size) < (addr + size))
    return ERR_PTR(-EINVAL);

    if (!can_do_mlock())


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