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    Subject[PATCH AUTOSEL for 4.9 231/281] skbuff: only inherit relevant tx_flags
    Date
    From: Willem de Bruijn <willemb@google.com>

    [ Upstream commit fff88030b3ff930ca7a3d74acfee0472f33887ea ]

    When inheriting tx_flags from one skbuff to another, always apply a
    mask to avoid overwriting unrelated other bits in the field.

    The two SKBTX_SHARED_FRAG cases clears all other bits. In practice,
    tx_flags are zero at this point now. But this is fragile. Timestamp
    flags are set, for instance, if in tcp_gso_segment, after this clear
    in skb_segment.

    The SKBTX_ANY_TSTAMP mask in __skb_tstamp_tx ensures that new
    skbs do not accidentally inherit flags such as SKBTX_SHARED_FRAG.

    Signed-off-by: Willem de Bruijn <willemb@google.com>
    Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
    Acked-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    net/core/skbuff.c | 10 ++++++----
    1 file changed, 6 insertions(+), 4 deletions(-)

    diff --git a/net/core/skbuff.c b/net/core/skbuff.c
    index 84725214ac5f..9c8636a10463 100644
    --- a/net/core/skbuff.c
    +++ b/net/core/skbuff.c
    @@ -2615,7 +2615,8 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len)
    {
    int pos = skb_headlen(skb);

    - skb_shinfo(skb1)->tx_flags = skb_shinfo(skb)->tx_flags & SKBTX_SHARED_FRAG;
    + skb_shinfo(skb1)->tx_flags |= skb_shinfo(skb)->tx_flags &
    + SKBTX_SHARED_FRAG;
    if (len < pos) /* Split line is inside header. */
    skb_split_inside_header(skb, skb1, len, pos);
    else /* Second chunk has no header, nothing to copy. */
    @@ -3228,8 +3229,8 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
    skb_copy_from_linear_data_offset(head_skb, offset,
    skb_put(nskb, hsize), hsize);

    - skb_shinfo(nskb)->tx_flags = skb_shinfo(head_skb)->tx_flags &
    - SKBTX_SHARED_FRAG;
    + skb_shinfo(nskb)->tx_flags |= skb_shinfo(head_skb)->tx_flags &
    + SKBTX_SHARED_FRAG;

    while (pos < offset + len) {
    if (i >= nfrags) {
    @@ -3881,7 +3882,8 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
    return;

    if (tsonly) {
    - skb_shinfo(skb)->tx_flags = skb_shinfo(orig_skb)->tx_flags;
    + skb_shinfo(skb)->tx_flags |= skb_shinfo(orig_skb)->tx_flags &
    + SKBTX_ANY_TSTAMP;
    skb_shinfo(skb)->tskey = skb_shinfo(orig_skb)->tskey;
    }

    --
    2.14.1
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