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    Subject[PATCH 5.11 088/329] ethtool: ioctl: Fix out-of-bounds warning in store_link_ksettings_for_user()
    Date
    From: Gustavo A. R. Silva <gustavoars@kernel.org>

    [ Upstream commit c1d9e34e11281a8ba1a1c54e4db554232a461488 ]

    Fix the following out-of-bounds warning:

    net/ethtool/ioctl.c:492:2: warning: 'memcpy' offset [49, 84] from the object at 'link_usettings' is out of the bounds of referenced subobject 'base' with type 'struct ethtool_link_settings' at offset 0 [-Warray-bounds]

    The problem is that the original code is trying to copy data into a
    some struct members adjacent to each other in a single call to
    memcpy(). This causes a legitimate compiler warning because memcpy()
    overruns the length of &link_usettings.base. Fix this by directly
    using &link_usettings and _from_ as destination and source addresses,
    instead.

    This helps with the ongoing efforts to globally enable -Warray-bounds
    and get us closer to being able to tighten the FORTIFY_SOURCE routines
    on memcpy().

    Link: https://github.com/KSPP/linux/issues/109
    Reported-by: kernel test robot <lkp@intel.com>
    Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/ethtool/ioctl.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
    index 771688e1b0da..2603966da904 100644
    --- a/net/ethtool/ioctl.c
    +++ b/net/ethtool/ioctl.c
    @@ -489,7 +489,7 @@ store_link_ksettings_for_user(void __user *to,
    {
    struct ethtool_link_usettings link_usettings;

    - memcpy(&link_usettings.base, &from->base, sizeof(link_usettings));
    + memcpy(&link_usettings, from, sizeof(link_usettings));
    bitmap_to_arr32(link_usettings.link_modes.supported,
    from->link_modes.supported,
    __ETHTOOL_LINK_MODE_MASK_NBITS);
    --
    2.30.2


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