cd35ef9149
For the non-XDP case, commit 773225388dae15e72790 ("net: thunderx: Optimize
page recycling for XDP") added code to nicvf_free_rbdr() that, when releasing
the additional receive buffer page reference held for recycling, repeatedly
calls put_page() until the page's _refcount goes to zero. Which results in
the page being freed.
This is not okay if the page's _refcount was greater than 1 (in the non-XDP
case), because nicvf_free_rbdr() should not be subtracting more than what
nicvf_alloc_page() had previously added to the page's _refcount, which was
only 1 (in the non-XDP case).
This can arise if a received packet is still being processed and the receive
buffer (i.e., skb->head) has not yet been freed via skb_free_head() when
nicvf_free_rbdr() is spinning through the aforementioned put_page() loop.
If this should occur, when the received packet finishes processing and
skb_free_head() is called, various problems can ensue. Exactly what, depends on
whether the page has already been reallocated or not, anything from "BUG: Bad
page state ... ", to "Unable to handle kernel NULL pointer dereference ..." or
"Unable to handle kernel paging request...".
So this patch changes nicvf_free_rbdr() to only call put_page() once for pages
held for recycling (in the non-XDP case).
Fixes: 773225388dae ("net: thunderx: Optimize page recycling for XDP")
Signed-off-by: Dean Nelson <dnelson@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.