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SubjectRe: [PATCH v3 2/3] mm/mempolicy: fix the check of nodemask from user
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On 11/17/2017 02:37 AM, Yisheng Xie wrote:
> As Xiaojun reported the ltp of migrate_pages01 will failed on ARCH 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] memtioned,
> 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
>
> Reported-by: Tan Xiaojun <tanxiaojun@huawei.com>
> Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> mm/mempolicy.c | 23 ++++++++++++++++++++---
> 1 file changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 6e867a8..65df28d 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1263,6 +1263,7 @@ 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;
>
> @@ -1279,11 +1280,17 @@ 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)) {
> 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) {
> @@ -1296,6 +1303,16 @@ 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;
>

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