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[ Upstream commitcd35ef9149] For the non-XDP case, commit773225388d("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:773225388d("net: thunderx: Optimize page recycling for XDP") Signed-off-by: Dean Nelson <dnelson@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.