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    Subject[PATCH AUTOSEL for 4.9 257/293] mm/mempolicy: fix the check of nodemask from user
    Date
    From: Yisheng Xie <xieyisheng1@huawei.com>

    [ Upstream commit 56521e7a02b7b84a5e72691a1fb15570e6055545 ]

    As Xiaojun reported the ltp of migrate_pages01 will fail on arm64 system
    which has 4 nodes[0...3], all have memory and CONFIG_NODES_SHIFT=2:

    migrate_pages01 0 TINFO : test_invalid_nodes
    migrate_pages01 14 TFAIL : migrate_pages_common.c:45: unexpected failure - returned value = 0, expected: -1
    migrate_pages01 15 TFAIL : migrate_pages_common.c:55: call succeeded unexpectedly

    In this case the test_invalid_nodes of migrate_pages01 will call:
    SYSC_migrate_pages as:

    migrate_pages(0, , {0x0000000000000001}, 64, , {0x0000000000000010}, 64) = 0

    The new nodes specifies one or more node IDs that are greater than the
    maximum supported node ID, however, the errno is not set to EINVAL as
    expected.

    As man pages of set_mempolicy[1], mbind[2], and migrate_pages[3]
    mentioned, when nodemask specifies one or more node IDs that are greater
    than the maximum supported node ID, the errno should set to EINVAL.
    However, get_nodes only check whether the part of bits
    [BITS_PER_LONG*BITS_TO_LONGS(MAX_NUMNODES), maxnode) is zero or not, and
    remain [MAX_NUMNODES, BITS_PER_LONG*BITS_TO_LONGS(MAX_NUMNODES)
    unchecked.

    This patch is to check the bits of [MAX_NUMNODES, maxnode) in get_nodes
    to let migrate_pages set the errno to EINVAL when nodemask specifies one
    or more node IDs that are greater than the maximum supported node ID,
    which follows the manpage's guide.

    [1] http://man7.org/linux/man-pages/man2/set_mempolicy.2.html
    [2] http://man7.org/linux/man-pages/man2/mbind.2.html
    [3] http://man7.org/linux/man-pages/man2/migrate_pages.2.html

    Link: http://lkml.kernel.org/r/1510882624-44342-3-git-send-email-xieyisheng1@huawei.com
    Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
    Reported-by: Tan Xiaojun <tanxiaojun@huawei.com>
    Acked-by: Vlastimil Babka <vbabka@suse.cz>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Chris Salls <salls@cs.ucsb.edu>
    Cc: Christopher Lameter <cl@linux.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    mm/mempolicy.c | 23 ++++++++++++++++++++---
    1 file changed, 20 insertions(+), 3 deletions(-)

    diff --git a/mm/mempolicy.c b/mm/mempolicy.c
    index a8ab5e73dc61..92f92f477304 100644
    --- a/mm/mempolicy.c
    +++ b/mm/mempolicy.c
    @@ -1264,6 +1264,7 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask,
    unsigned long maxnode)
    {
    unsigned long k;
    + unsigned long t;
    unsigned long nlongs;
    unsigned long endmask;

    @@ -1280,13 +1281,19 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask,
    else
    endmask = (1UL << (maxnode % BITS_PER_LONG)) - 1;

    - /* When the user specified more nodes than supported just check
    - if the non supported part is all zero. */
    + /*
    + * When the user specified more nodes than supported just check
    + * if the non supported part is all zero.
    + *
    + * If maxnode have more longs than MAX_NUMNODES, check
    + * the bits in that area first. And then go through to
    + * check the rest bits which equal or bigger than MAX_NUMNODES.
    + * Otherwise, just check bits [MAX_NUMNODES, maxnode).
    + */
    if (nlongs > BITS_TO_LONGS(MAX_NUMNODES)) {
    if (nlongs > PAGE_SIZE/sizeof(long))
    return -EINVAL;
    for (k = BITS_TO_LONGS(MAX_NUMNODES); k < nlongs; k++) {
    - unsigned long t;
    if (get_user(t, nmask + k))
    return -EFAULT;
    if (k == nlongs - 1) {
    @@ -1299,6 +1306,16 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask,
    endmask = ~0UL;
    }

    + if (maxnode > MAX_NUMNODES && MAX_NUMNODES % BITS_PER_LONG != 0) {
    + unsigned long valid_mask = endmask;
    +
    + valid_mask &= ~((1UL << (MAX_NUMNODES % BITS_PER_LONG)) - 1);
    + if (get_user(t, nmask + nlongs - 1))
    + return -EFAULT;
    + if (t & valid_mask)
    + return -EINVAL;
    + }
    +
    if (copy_from_user(nodes_addr(*nodes), nmask, nlongs*sizeof(unsigned long)))
    return -EFAULT;
    nodes_addr(*nodes)[nlongs-1] &= endmask;
    --
    2.15.1
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