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    Subject[PATCH 4.4 109/112] ath10k: check idx validity in __ath10k_htt_rx_ring_fill_n()
    Date
    From: Zekun Shen <bruceshenzk@gmail.com>

    [ Upstream commit bad60b8d1a7194df38fd7fe4b22f3f4dcf775099 ]

    The idx in __ath10k_htt_rx_ring_fill_n function lives in
    consistent dma region writable by the device. Malfunctional
    or malicious device could manipulate such idx to have a OOB
    write. Either by
    htt->rx_ring.netbufs_ring[idx] = skb;
    or by
    ath10k_htt_set_paddrs_ring(htt, paddr, idx);

    The idx can also be negative as it's signed, giving a large
    memory space to write to.

    It's possibly exploitable by corruptting a legit pointer with
    a skb pointer. And then fill skb with payload as rougue object.

    Part of the log here. Sometimes it appears as UAF when writing
    to a freed memory by chance.

    [ 15.594376] BUG: unable to handle page fault for address: ffff887f5c1804f0
    [ 15.595483] #PF: supervisor write access in kernel mode
    [ 15.596250] #PF: error_code(0x0002) - not-present page
    [ 15.597013] PGD 0 P4D 0
    [ 15.597395] Oops: 0002 [#1] SMP KASAN PTI
    [ 15.597967] CPU: 0 PID: 82 Comm: kworker/u2:2 Not tainted 5.6.0 #69
    [ 15.598843] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
    BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
    [ 15.600438] Workqueue: ath10k_wq ath10k_core_register_work [ath10k_core]
    [ 15.601389] RIP: 0010:__ath10k_htt_rx_ring_fill_n
    (linux/drivers/net/wireless/ath/ath10k/htt_rx.c:173) ath10k_core

    Signed-off-by: Zekun Shen <bruceshenzk@gmail.com>
    Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
    Link: https://lore.kernel.org/r/20200623221105.3486-1-bruceshenzk@gmail.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/wireless/ath/ath10k/htt_rx.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    diff --git a/drivers/net/wireless/ath/ath10k/htt_rx.c b/drivers/net/wireless/ath/ath10k/htt_rx.c
    index a65b5d7f59f44..1c6c422dbad64 100644
    --- a/drivers/net/wireless/ath/ath10k/htt_rx.c
    +++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
    @@ -99,6 +99,14 @@ static int __ath10k_htt_rx_ring_fill_n(struct ath10k_htt *htt, int num)
    BUILD_BUG_ON(HTT_RX_RING_FILL_LEVEL >= HTT_RX_RING_SIZE / 2);

    idx = __le32_to_cpu(*htt->rx_ring.alloc_idx.vaddr);
    +
    + if (idx < 0 || idx >= htt->rx_ring.size) {
    + ath10k_err(htt->ar, "rx ring index is not valid, firmware malfunctioning?\n");
    + idx &= htt->rx_ring.size_mask;
    + ret = -ENOMEM;
    + goto fail;
    + }
    +
    while (num > 0) {
    skb = dev_alloc_skb(HTT_RX_BUF_SIZE + HTT_RX_DESC_ALIGN);
    if (!skb) {
    --
    2.25.1


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