AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

In the Linux kernel, the following vulnerability has been resolved:

net: tls: fix off-by-one in sg_chain entry count for wrapped sk_msg ring

When an sk_msg scatterlist ring wraps (sg.end < sg.start),
tls_push_record() chains the tail portion of the ring to the head
using sg_chain(). An extra entry in the sg array is reserved for
this:

  struct sk_msg_sg {
        [...]
        /* The extra two elements:
         * 1) used for chaining the front and sections when the list becomes
         *    partitioned (e.g. end < start). The crypto APIs require the
         *    chaining;
         * 2) to chain tailer SG entries after the message.
         */
        struct scatterlist              data[MAX_MSG_FRAGS + 2];

The current code uses MAX_SKB_FRAGS + 1 as the ring size:

    sg_chain(&msg_pl->sg.data[msg_pl->sg.start],
             MAX_SKB_FRAGS - msg_pl->sg.start + 1,
             msg_pl->sg.data);

This places the chain pointer at

  sg_chain(data[start], (MAX_SKB_FRAGS - msg_start + 1) .. =
  &data[start] + (MAX_SKB_FRAGS - msg_start + 1) - 1 =
  data[start + (MAX_SKB_FRAGS - start + 1) - 1] =
  data[MAX_SKB_FRAGS]

instead of the true last entry. This is likely due to a "race" of
the commit under Fixes landing close to
commit 031097d9e079 ("bpf: sk_msg, zap ingress queue on psock down")

Convert to ARRAY_SIZE and drop the data[start] / - start (as suggested
by Sabrina).

https://git.kernel.org/stable/c/131ef12057d92b77b636321b7849c69222405a97

https://git.kernel.org/stable/c/285943c6e7ca309bbea84b253745154241d9788a

https://git.kernel.org/stable/c/2fb0dc7e0099686c4e9d2732745d8a31b18c3628

https://git.kernel.org/stable/c/47110c3a9ac247b688657337f5981efcfcb240dc

https://git.kernel.org/stable/c/66339b71f105e6f83e0da3b9583d95077534fe1d

https://git.kernel.org/stable/c/73963a375885d5ccb7def39fd0b4f542e0f343dd

https://git.kernel.org/stable/c/84158c2997159df4a0d70cd9c46774512d32a522

https://git.kernel.org/stable/c/eca989eab4b2599dcb02f72140a7c08f08838520

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