CVE-2021-47587

In the Linux kernel, the following vulnerability has been resolved: net:
systemport: Add global locking for descriptor lifecycle The descriptor list
is a shared resource across all of the transmit queues, and the locking
mechanism used today only protects concurrency across a given transmit
queue between the transmit and reclaiming. This creates an opportunity for
the SYSTEMPORT hardware to work on corrupted descriptors if we have
multiple producers at once which is the case when using multiple transmit
queues. This was particularly noticeable when using multiple flows/transmit
queues and it showed up in interesting ways in that UDP packets would get a
correct UDP header checksum being calculated over an incorrect packet
length. Similarly TCP packets would get an equally correct checksum
computed by the hardware over an incorrect packet length. The SYSTEMPORT
hardware maintains an internal descriptor list that it re-arranges when the
driver produces a new descriptor anytime it writes to the
WRITE_PORT_{HI,LO} registers, there is however some delay in the hardware
to re-organize its descriptors and it is possible that concurrent TX queues
eventually break this internal allocation scheme to the point where the
length/status part of the descriptor gets used for an incorrect data
buffer. The fix is to impose a global serialization for all TX queues in
the short section where we are writing to the WRITE_PORT_{HI,LO} registers
which solves the corruption even with multiple concurrent TX queues being
used.