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    Subject[PATCH 5.4 58/60] net/rds: restrict iovecs length for RDS_CMSG_RDMA_ARGS
    Date
    From: Sabyrzhan Tasbolatov <snovitoll@gmail.com>

    commit a11148e6fcce2ae53f47f0a442d098d860b4f7db upstream.

    syzbot found WARNING in rds_rdma_extra_size [1] when RDS_CMSG_RDMA_ARGS
    control message is passed with user-controlled
    0x40001 bytes of args->nr_local, causing order >= MAX_ORDER condition.

    The exact value 0x40001 can be checked with UIO_MAXIOV which is 0x400.
    So for kcalloc() 0x400 iovecs with sizeof(struct rds_iovec) = 0x10
    is the closest limit, with 0x10 leftover.

    Same condition is currently done in rds_cmsg_rdma_args().

    [1] WARNING: mm/page_alloc.c:5011
    [..]
    Call Trace:
    alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2267
    alloc_pages include/linux/gfp.h:547 [inline]
    kmalloc_order+0x2e/0xb0 mm/slab_common.c:837
    kmalloc_order_trace+0x14/0x120 mm/slab_common.c:853
    kmalloc_array include/linux/slab.h:592 [inline]
    kcalloc include/linux/slab.h:621 [inline]
    rds_rdma_extra_size+0xb2/0x3b0 net/rds/rdma.c:568
    rds_rm_size net/rds/send.c:928 [inline]

    Reported-by: syzbot+1bd2b07f93745fa38425@syzkaller.appspotmail.com
    Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
    Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
    Link: https://lore.kernel.org/r/20210201203233.1324704-1-snovitoll@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/rds/rdma.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/net/rds/rdma.c
    +++ b/net/rds/rdma.c
    @@ -532,6 +532,9 @@ int rds_rdma_extra_size(struct rds_rdma_
    if (args->nr_local == 0)
    return -EINVAL;

    + if (args->nr_local > UIO_MAXIOV)
    + return -EMSGSIZE;
    +
    iov->iov = kcalloc(args->nr_local,
    sizeof(struct rds_iovec),
    GFP_KERNEL);

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