5.0-stable review patch. If anyone has any objections, please let me know.
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From: Dean Nelson dnelson@redhat.com
[ Upstream commit cd35ef91490ad8049dd180bb060aff7ee192eda9 ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/ethernet/cavium/thunder/nicvf_queues.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
--- a/drivers/net/ethernet/cavium/thunder/nicvf_queues.c +++ b/drivers/net/ethernet/cavium/thunder/nicvf_queues.c @@ -364,11 +364,10 @@ static void nicvf_free_rbdr(struct nicvf while (head < rbdr->pgcnt) { pgcache = &rbdr->pgcache[head]; if (pgcache->page && page_ref_count(pgcache->page) != 0) { - if (!rbdr->is_xdp) { - put_page(pgcache->page); - continue; + if (rbdr->is_xdp) { + page_ref_sub(pgcache->page, + pgcache->ref_count - 1); } - page_ref_sub(pgcache->page, pgcache->ref_count - 1); put_page(pgcache->page); } head++;