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    Subject[PATCH 5.4 02/19] AX.25: Prevent out-of-bounds read in ax25_sendmsg()
    Date
    From: Peilin Ye <yepeilin.cs@gmail.com>

    [ Upstream commit 8885bb0621f01a6c82be60a91e5fc0f6e2f71186 ]

    Checks on `addr_len` and `usax->sax25_ndigis` are insufficient.
    ax25_sendmsg() can go out of bounds when `usax->sax25_ndigis` equals to 7
    or 8. Fix it.

    It is safe to remove `usax->sax25_ndigis > AX25_MAX_DIGIS`, since
    `addr_len` is guaranteed to be less than or equal to
    `sizeof(struct full_sockaddr_ax25)`

    Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ax25/af_ax25.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/net/ax25/af_ax25.c
    +++ b/net/ax25/af_ax25.c
    @@ -1509,7 +1509,8 @@ static int ax25_sendmsg(struct socket *s
    struct full_sockaddr_ax25 *fsa = (struct full_sockaddr_ax25 *)usax;

    /* Valid number of digipeaters ? */
    - if (usax->sax25_ndigis < 1 || usax->sax25_ndigis > AX25_MAX_DIGIS) {
    + if (usax->sax25_ndigis < 1 || addr_len < sizeof(struct sockaddr_ax25) +
    + sizeof(ax25_address) * usax->sax25_ndigis) {
    err = -EINVAL;
    goto out;
    }

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