kernel/linux.git/net/core/page_pool.c, branch v6.12.80

page_pool: Clamp pool size to max 16K pages

2025-11-13T20:34:31+00:00

[ Upstream commit a1b501a8c6a87c9265fd03bd004035199e2e8128 ] page_pool_init() returns E2BIG when the page_pool size goes above 32K pages. As some drivers are configuring the page_pool size according to the MTU and ring size, there are cases where this limit is exceeded and the queue creation fails. The page_pool size doesn't have to cover a full queue, especially for larger ring size. So clamp the size instead of returning an error. Do this in the core to avoid having each driver do the clamping. The current limit was deemed to high [1] so it was reduced to 16K to avoid page waste. [1] https://lore.kernel.org/all/1758532715-820422-3-git-send-email-tariqt@nvidia.com/ Signed-off-by: Dragos Tatulea Reviewed-by: Tariq Toukan Link: https://patch.msgid.link/20250926131605.2276734-2-dtatulea@nvidia.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

page_pool: always add GFP_NOWARN for ATOMIC allocations

2025-11-13T20:34:25+00:00

[ Upstream commit f3b52167a0cb23b27414452fbc1278da2ee884fc ] Driver authors often forget to add GFP_NOWARN for page allocation from the datapath. This is annoying to users as OOMs are a fact of life, and we pretty much expect network Rx to hit page allocation failures during OOM. Make page pool add GFP_NOWARN for ATOMIC allocations by default. Reviewed-by: Mina Almasry Link: https://patch.msgid.link/20250912161703.361272-1-kuba@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

page_pool: Fix PP_MAGIC_MASK to avoid crashing on some 32-bit arches

2025-10-19T14:33:34+00:00

commit 95920c2ed02bde551ab654e9749c2ca7bc3100e0 upstream. Helge reported that the introduction of PP_MAGIC_MASK let to crashes on boot on his 32-bit parisc machine. The cause of this is the mask is set too wide, so the page_pool_page_is_pp() incurs false positives which crashes the machine. Just disabling the check in page_pool_is_pp() will lead to the page_pool code itself malfunctioning; so instead of doing this, this patch changes the define for PP_DMA_INDEX_BITS to avoid mistaking arbitrary kernel pointers for page_pool-tagged pages. The fix relies on the kernel pointers that alias with the pp_magic field always being above PAGE_OFFSET. With this assumption, we can use the lowest bit of the value of PAGE_OFFSET as the upper bound of the PP_DMA_INDEX_MASK, which should avoid the false positives. Because we cannot rely on PAGE_OFFSET always being a compile-time constant, nor on it always being >0, we fall back to disabling the dma_index storage when there are not enough bits available. This leaves us in the situation we were in before the patch in the Fixes tag, but only on a subset of architecture configurations. This seems to be the best we can do until the transition to page types in complete for page_pool pages. v2: - Make sure there's at least 8 bits available and that the PAGE_OFFSET bit calculation doesn't wrap Link: https://lore.kernel.org/all/aMNJMFa5fDalFmtn@p100/ Fixes: ee62ce7a1d90 ("page_pool: Track DMA-mapped pages and unmap them when destroying the pool") Cc: stable@vger.kernel.org # 6.15+ Tested-by: Helge Deller Signed-off-by: Toke Høiland-Jørgensen Reviewed-by: Mina Almasry Tested-by: Helge Deller Link: https://patch.msgid.link/20250930114331.675412-1-toke@redhat.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

net: page_pool: Don't recycle into cache on PREEMPT_RT

2025-06-27T10:11:30+00:00

[ Upstream commit 32471b2f481dea8624f27669d36ffd131d24b732 ] With preemptible softirq and no per-CPU locking in local_bh_disable() on PREEMPT_RT the consumer can be preempted while a skb is returned. Avoid the race by disabling the recycle into the cache on PREEMPT_RT. Cc: Jesper Dangaard Brouer Cc: Ilias Apalodimas Signed-off-by: Sebastian Andrzej Siewior Link: https://patch.msgid.link/20250512092736.229935-2-bigeasy@linutronix.de Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

page_pool: Fix use-after-free in page_pool_recycle_in_ring

2025-06-19T13:32:14+00:00

[ Upstream commit 271683bb2cf32e5126c592b5d5e6a756fa374fd9 ] syzbot reported a uaf in page_pool_recycle_in_ring: BUG: KASAN: slab-use-after-free in lock_release+0x151/0xa30 kernel/locking/lockdep.c:5862 Read of size 8 at addr ffff8880286045a0 by task syz.0.284/6943 CPU: 0 UID: 0 PID: 6943 Comm: syz.0.284 Not tainted 6.13.0-rc3-syzkaller-gdfa94ce54f41 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0x169/0x550 mm/kasan/report.c:489 kasan_report+0x143/0x180 mm/kasan/report.c:602 lock_release+0x151/0xa30 kernel/locking/lockdep.c:5862 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:165 [inline] _raw_spin_unlock_bh+0x1b/0x40 kernel/locking/spinlock.c:210 spin_unlock_bh include/linux/spinlock.h:396 [inline] ptr_ring_produce_bh include/linux/ptr_ring.h:164 [inline] page_pool_recycle_in_ring net/core/page_pool.c:707 [inline] page_pool_put_unrefed_netmem+0x748/0xb00 net/core/page_pool.c:826 page_pool_put_netmem include/net/page_pool/helpers.h:323 [inline] page_pool_put_full_netmem include/net/page_pool/helpers.h:353 [inline] napi_pp_put_page+0x149/0x2b0 net/core/skbuff.c:1036 skb_pp_recycle net/core/skbuff.c:1047 [inline] skb_free_head net/core/skbuff.c:1094 [inline] skb_release_data+0x6c4/0x8a0 net/core/skbuff.c:1125 skb_release_all net/core/skbuff.c:1190 [inline] __kfree_skb net/core/skbuff.c:1204 [inline] sk_skb_reason_drop+0x1c9/0x380 net/core/skbuff.c:1242 kfree_skb_reason include/linux/skbuff.h:1263 [inline] __skb_queue_purge_reason include/linux/skbuff.h:3343 [inline] root cause is: page_pool_recycle_in_ring ptr_ring_produce spin_lock(&r->producer_lock); WRITE_ONCE(r->queue[r->producer++], ptr) //recycle last page to pool page_pool_release page_pool_scrub page_pool_empty_ring ptr_ring_consume page_pool_return_page //release all page __page_pool_destroy free_percpu(pool->recycle_stats); free(pool) //free spin_unlock(&r->producer_lock); //pool->ring uaf read recycle_stat_inc(pool, ring); page_pool can be free while page pool recycle the last page in ring. Add producer-lock barrier to page_pool_release to prevent the page pool from being free before all pages have been recycled. recycle_stat_inc() is empty when CONFIG_PAGE_POOL_STATS is not enabled, which will trigger Wempty-body build warning. Add definition for pool stat macro to fix warning. Suggested-by: Jakub Kicinski Link: https://lore.kernel.org/netdev/20250513083123.3514193-1-dongchenchen2@huawei.com Fixes: ff7d6b27f894 ("page_pool: refurbish version of page_pool code") Reported-by: syzbot+204a4382fcb3311f3858@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=204a4382fcb3311f3858 Signed-off-by: Dong Chenchen Reviewed-by: Toke Høiland-Jørgensen Reviewed-by: Mina Almasry Link: https://patch.msgid.link/20250527114152.3119109-1-dongchenchen2@huawei.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

page_pool: Track DMA-mapped pages and unmap them when destroying the pool

2025-06-19T13:31:42+00:00

[ Upstream commit ee62ce7a1d909ccba0399680a03c2dee83bcae95 ] When enabling DMA mapping in page_pool, pages are kept DMA mapped until they are released from the pool, to avoid the overhead of re-mapping the pages every time they are used. This causes resource leaks and/or crashes when there are pages still outstanding while the device is torn down, because page_pool will attempt an unmap through a non-existent DMA device on the subsequent page return. To fix this, implement a simple tracking of outstanding DMA-mapped pages in page pool using an xarray. This was first suggested by Mina[0], and turns out to be fairly straight forward: We simply store pointers to pages directly in the xarray with xa_alloc() when they are first DMA mapped, and remove them from the array on unmap. Then, when a page pool is torn down, it can simply walk the xarray and unmap all pages still present there before returning, which also allows us to get rid of the get/put_device() calls in page_pool. Using xa_cmpxchg(), no additional synchronisation is needed, as a page will only ever be unmapped once. To avoid having to walk the entire xarray on unmap to find the page reference, we stash the ID assigned by xa_alloc() into the page structure itself, using the upper bits of the pp_magic field. This requires a couple of defines to avoid conflicting with the POINTER_POISON_DELTA define, but this is all evaluated at compile-time, so does not affect run-time performance. The bitmap calculations in this patch gives the following number of bits for different architectures: - 23 bits on 32-bit architectures - 21 bits on PPC64 (because of the definition of ILLEGAL_POINTER_VALUE) - 32 bits on other 64-bit architectures Stashing a value into the unused bits of pp_magic does have the effect that it can make the value stored there lie outside the unmappable range (as governed by the mmap_min_addr sysctl), for architectures that don't define ILLEGAL_POINTER_VALUE. This means that if one of the pointers that is aliased to the pp_magic field (such as page->lru.next) is dereferenced while the page is owned by page_pool, that could lead to a dereference into userspace, which is a security concern. The risk of this is mitigated by the fact that (a) we always clear pp_magic before releasing a page from page_pool, and (b) this would need a use-after-free bug for struct page, which can have many other risks since page->lru.next is used as a generic list pointer in multiple places in the kernel. As such, with this patch we take the position that this risk is negligible in practice. For more discussion, see[1]. Since all the tracking added in this patch is performed on DMA map/unmap, no additional code is needed in the fast path, meaning the performance overhead of this tracking is negligible there. A micro-benchmark shows that the total overhead of the tracking itself is about 400 ns (39 cycles(tsc) 395.218 ns; sum for both map and unmap[2]). Since this cost is only paid on DMA map and unmap, it seems like an acceptable cost to fix the late unmap issue. Further optimisation can narrow the cases where this cost is paid (for instance by eliding the tracking when DMA map/unmap is a no-op). The extra memory needed to track the pages is neatly encapsulated inside xarray, which uses the 'struct xa_node' structure to track items. This structure is 576 bytes long, with slots for 64 items, meaning that a full node occurs only 9 bytes of overhead per slot it tracks (in practice, it probably won't be this efficient, but in any case it should be an acceptable overhead). [0] https://lore.kernel.org/all/CAHS8izPg7B5DwKfSuzz-iOop_YRbk3Sd6Y4rX7KBG9DcVJcyWg@mail.gmail.com/ [1] https://lore.kernel.org/r/20250320023202.GA25514@openwall.com [2] https://lore.kernel.org/r/ae07144c-9295-4c9d-a400-153bb689fe9e@huawei.com Reported-by: Yonglong Liu Closes: https://lore.kernel.org/r/8743264a-9700-4227-a556-5f931c720211@huawei.com Fixes: ff7d6b27f894 ("page_pool: refurbish version of page_pool code") Suggested-by: Mina Almasry Reviewed-by: Mina Almasry Reviewed-by: Jesper Dangaard Brouer Tested-by: Jesper Dangaard Brouer Tested-by: Qiuling Ren Tested-by: Yuying Ma Tested-by: Yonglong Liu Acked-by: Jesper Dangaard Brouer Signed-off-by: Toke Høiland-Jørgensen Link: https://patch.msgid.link/20250409-page-pool-track-dma-v9-2-6a9ef2e0cba8@redhat.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: page_pool: avoid false positive warning if NAPI was never added

2025-05-29T09:02:59+00:00

[ Upstream commit c1e00bc4be06cacee6307cedb9b55bbaddb5044d ] We expect NAPI to be in disabled state when page pool is torn down. But it is also legal if the NAPI is completely uninitialized. Reviewed-by: Mina Almasry Link: https://patch.msgid.link/20250206225638.1387810-4-kuba@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

page_pool: avoid infinite loop to schedule delayed worker

2025-04-20T08:15:18+00:00

[ Upstream commit 43130d02baa137033c25297aaae95fd0edc41654 ] We noticed the kworker in page_pool_release_retry() was waken up repeatedly and infinitely in production because of the buggy driver causing the inflight less than 0 and warning us in page_pool_inflight()[1]. Since the inflight value goes negative, it means we should not expect the whole page_pool to get back to work normally. This patch mitigates the adverse effect by not rescheduling the kworker when detecting the inflight negative in page_pool_release_retry(). [1] [Mon Feb 10 20:36:11 2025] ------------[ cut here ]------------ [Mon Feb 10 20:36:11 2025] Negative(-51446) inflight packet-pages ... [Mon Feb 10 20:36:11 2025] Call Trace: [Mon Feb 10 20:36:11 2025] page_pool_release_retry+0x23/0x70 [Mon Feb 10 20:36:11 2025] process_one_work+0x1b1/0x370 [Mon Feb 10 20:36:11 2025] worker_thread+0x37/0x3a0 [Mon Feb 10 20:36:11 2025] kthread+0x11a/0x140 [Mon Feb 10 20:36:11 2025] ? process_one_work+0x370/0x370 [Mon Feb 10 20:36:11 2025] ? __kthread_cancel_work+0x40/0x40 [Mon Feb 10 20:36:11 2025] ret_from_fork+0x35/0x40 [Mon Feb 10 20:36:11 2025] ---[ end trace ebffe800f33e7e34 ]--- Note: before this patch, the above calltrace would flood the dmesg due to repeated reschedule of release_dw kworker. Signed-off-by: Jason Xing Reviewed-by: Mina Almasry Link: https://patch.msgid.link/20250214064250.85987-1-kerneljasonxing@gmail.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

memory-provider: dmabuf devmem memory provider

2024-09-12T03:44:31+00:00

Implement a memory provider that allocates dmabuf devmem in the form of net_iov. The provider receives a reference to the struct netdev_dmabuf_binding via the pool->mp_priv pointer. The driver needs to set this pointer for the provider in the net_iov. The provider obtains a reference on the netdev_dmabuf_binding which guarantees the binding and the underlying mapping remains alive until the provider is destroyed. Usage of PP_FLAG_DMA_MAP is required for this memory provide such that the page_pool can provide the driver with the dma-addrs of the devmem. Support for PP_FLAG_DMA_SYNC_DEV is omitted for simplicity & p.order != 0. Signed-off-by: Willem de Bruijn Signed-off-by: Kaiyuan Zhang Signed-off-by: Mina Almasry Reviewed-by: Pavel Begunkov Reviewed-by: Jakub Kicinski Link: https://patch.msgid.link/20240910171458.219195-7-almasrymina@google.com Signed-off-by: Jakub Kicinski

page_pool: devmem support

2024-09-12T03:44:31+00:00

Convert netmem to be a union of struct page and struct netmem. Overload the LSB of struct netmem* to indicate that it's a net_iov, otherwise it's a page. Currently these entries in struct page are rented by the page_pool and used exclusively by the net stack: struct { unsigned long pp_magic; struct page_pool *pp; unsigned long _pp_mapping_pad; unsigned long dma_addr; atomic_long_t pp_ref_count; }; Mirror these (and only these) entries into struct net_iov and implement netmem helpers that can access these common fields regardless of whether the underlying type is page or net_iov. Implement checks for net_iov in netmem helpers which delegate to mm APIs, to ensure net_iov are never passed to the mm stack. Signed-off-by: Mina Almasry Reviewed-by: Pavel Begunkov Acked-by: Jakub Kicinski Link: https://patch.msgid.link/20240910171458.219195-6-almasrymina@google.com Signed-off-by: Jakub Kicinski