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(-)
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;
--
2.33.0On 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
>
>
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