| Message ID | 20241022032214.3915232-3-linyunsheng@huawei.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | fix two bugs related to page_pool | expand |
On Tue, 22 Oct 2024 11:22:12 +0800, Yunsheng Lin <linyunsheng@huawei.com> wrote: > page_pool page may be freed from skb_defer_free_flush() in > softirq context without binding to any specific napi, it > may cause use-after-free problem due to the below time window, > as below, CPU1 may still access napi->list_owner after CPU0 > free the napi memory: > > CPU 0 CPU1 > page_pool_destroy() skb_defer_free_flush() > . . > . napi = READ_ONCE(pool->p.napi); > . . > page_pool_disable_direct_recycling() . > driver free napi memory . > . . > . napi && READ_ONCE(napi->list_owner) == cpuid > . . > > Use rcu mechanism to avoid the above problem. > > Note, the above was found during code reviewing on how to fix > the problem in [1]. > > 1. https://lore.kernel.org/lkml/8067f204-1380-4d37-8ffd-007fc6f26738@kernel.org/T/ > > Fixes: dd64b232deb8 ("page_pool: unlink from napi during destroy") > Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com> Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > CC: Alexander Lobakin <aleksander.lobakin@intel.com> > --- > As the IOMMU fix patch depends on synchronize_rcu() added in this > patch and the time window is so small that it doesn't seem to be > an urgent fix, so target the net-next as the IOMMU fix patch does. > --- > net/core/page_pool.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > index a813d30d2135..dd497f5c927d 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -795,6 +795,7 @@ __page_pool_put_page(struct page_pool *pool, netmem_ref netmem, > static bool page_pool_napi_local(const struct page_pool *pool) > { > const struct napi_struct *napi; > + bool napi_local; > u32 cpuid; > > if (unlikely(!in_softirq())) > @@ -810,9 +811,15 @@ static bool page_pool_napi_local(const struct page_pool *pool) > if (READ_ONCE(pool->cpuid) == cpuid) > return true; > > + /* Synchronizated with page_pool_destory() to avoid use-after-free > + * for 'napi'. > + */ > + rcu_read_lock(); > napi = READ_ONCE(pool->p.napi); > + napi_local = napi && READ_ONCE(napi->list_owner) == cpuid; > + rcu_read_unlock(); > > - return napi && READ_ONCE(napi->list_owner) == cpuid; > + return napi_local; > } > > void page_pool_put_unrefed_netmem(struct page_pool *pool, netmem_ref netmem, > @@ -1126,6 +1133,12 @@ void page_pool_destroy(struct page_pool *pool) > if (!page_pool_release(pool)) > return; > > + /* Paired with rcu lock in page_pool_napi_local() to enable clearing > + * of pool->p.napi in page_pool_disable_direct_recycling() is seen > + * before returning to driver to free the napi instance. > + */ > + synchronize_rcu(); > + > page_pool_detached(pool); > pool->defer_start = jiffies; > pool->defer_warn = jiffies + DEFER_WARN_INTERVAL; > -- > 2.33.0 > >
diff --git a/net/core/page_pool.c b/net/core/page_pool.c index a813d30d2135..dd497f5c927d 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -795,6 +795,7 @@ __page_pool_put_page(struct page_pool *pool, netmem_ref netmem, static bool page_pool_napi_local(const struct page_pool *pool) { const struct napi_struct *napi; + bool napi_local; u32 cpuid; if (unlikely(!in_softirq())) @@ -810,9 +811,15 @@ static bool page_pool_napi_local(const struct page_pool *pool) if (READ_ONCE(pool->cpuid) == cpuid) return true; + /* Synchronizated with page_pool_destory() to avoid use-after-free + * for 'napi'. + */ + rcu_read_lock(); napi = READ_ONCE(pool->p.napi); + napi_local = napi && READ_ONCE(napi->list_owner) == cpuid; + rcu_read_unlock(); - return napi && READ_ONCE(napi->list_owner) == cpuid; + return napi_local; } void page_pool_put_unrefed_netmem(struct page_pool *pool, netmem_ref netmem, @@ -1126,6 +1133,12 @@ void page_pool_destroy(struct page_pool *pool) if (!page_pool_release(pool)) return; + /* Paired with rcu lock in page_pool_napi_local() to enable clearing + * of pool->p.napi in page_pool_disable_direct_recycling() is seen + * before returning to driver to free the napi instance. + */ + synchronize_rcu(); + page_pool_detached(pool); pool->defer_start = jiffies; pool->defer_warn = jiffies + DEFER_WARN_INTERVAL;
page_pool page may be freed from skb_defer_free_flush() in softirq context without binding to any specific napi, it may cause use-after-free problem due to the below time window, as below, CPU1 may still access napi->list_owner after CPU0 free the napi memory: CPU 0 CPU1 page_pool_destroy() skb_defer_free_flush() . . . napi = READ_ONCE(pool->p.napi); . . page_pool_disable_direct_recycling() . driver free napi memory . . . . napi && READ_ONCE(napi->list_owner) == cpuid . . Use rcu mechanism to avoid the above problem. Note, the above was found during code reviewing on how to fix the problem in [1]. 1. https://lore.kernel.org/lkml/8067f204-1380-4d37-8ffd-007fc6f26738@kernel.org/T/ Fixes: dd64b232deb8 ("page_pool: unlink from napi during destroy") Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com> CC: Alexander Lobakin <aleksander.lobakin@intel.com> --- As the IOMMU fix patch depends on synchronize_rcu() added in this patch and the time window is so small that it doesn't seem to be an urgent fix, so target the net-next as the IOMMU fix patch does. --- net/core/page_pool.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)