Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: - [High] netdevsim: UAF in page_pool async destruction due to freed nsim_bus_dev - [Medium] netdevsim: memory leak and page_pool release loop in nsim_pp_hold_write --
commit 3929ee46c506ebcd379657adcaaf3d764e577c6d Author: Mina Almasry <[email protected]> netdevsim: support devmem RX and TX bindings This patch sets a 64-bit DMA mask on nsim_bus_dev, enables NETMEM_TX_DMA, and configures page_pool instances with PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, and PP_FLAG_ALLOW_UNREADABLE_NETMEM to allow testing of devmem bind operations in software selftests. > diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c > index b4a99f3ceac60..4415dc01c610b 100644 > --- a/drivers/net/netdevsim/netdev.c > +++ b/drivers/net/netdevsim/netdev.c [ ... ] > @@ -414,16 +414,22 @@ static int nsim_poll(struct napi_struct *napi, int > budget) > return done; > } > > -static int nsim_create_page_pool(struct page_pool **p, struct napi_struct > *napi) > +static int nsim_create_page_pool(struct net_device *dev, struct page_pool > **p, > + struct napi_struct *napi, int idx) > { > + struct netdevsim *ns = netdev_priv(dev); > struct page_pool_params params = { > .order = 0, > .pool_size = NSIM_RING_SIZE, > + .flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV | > + PP_FLAG_ALLOW_UNREADABLE_NETMEM, [Severity: Medium] Does adding PP_FLAG_ALLOW_UNREADABLE_NETMEM here cause a memory leak when used with the debugfs pp_hold file? When devmem is bound, a user writing to pp_hold triggers nsim_pp_hold_write() which attempts to allocate a page: nsim_pp_hold_write() { ... } else if (val) { ns->page = page_pool_dev_alloc_pages(ns->rq[0]->page_pool); if (!ns->page) ret = -ENOMEM; ... } Because the page pool is configured to allow unreadable devmem, page_pool_dev_alloc_pages() returns an unreadable devmem net_iov. The inline function netmem_to_page() detects it is unreadable and returns NULL. nsim_pp_hold_write() sees the NULL, treats it as an allocation failure, and drops the pointer without releasing the underlying net_iov back to the page pool. This leaks the inflight netmem, and later causes the page pool teardown workqueue (page_pool_release_retry) to spin indefinitely. > + .max_len = PAGE_SIZE, > .nid = NUMA_NO_NODE, > - .dev = &napi->dev->dev, > + .dev = &ns->nsim_bus_dev->dev, [Severity: High] Can this lead to a use-after-free during asynchronous page pool destruction? This sets the pool's device pointer to the dynamically allocated nsim_bus_dev, but the page pool does not appear to take a reference to it. If the netdevsim device is unregistered (e.g., via sysfs) while normal SKBs are still inflight in a socket receive queue, nsim_bus_dev's refcount can drop to 0, causing it to be synchronously freed: nsim_bus_dev_release() { ... nsim_bus_dev = container_of(dev, struct nsim_bus_dev, dev); kfree(nsim_bus_dev); } When those inflight SKBs are eventually consumed and freed by user-space, the asynchronous page pool destruction will invoke __page_pool_unmap_netmem_dma(), which calls dma_unmap_page_attrs(pool->p.dev, ...). Because pool->p.dev points to the already-freed nsim_bus_dev->dev, this results in a use-after-free. > + .napi = napi, > .dma_dir = DMA_BIDIRECTIONAL, > - .netdev = napi->dev, > + .netdev = dev, > + .queue_idx = idx, > }; -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=3
