linux-kernel - RE: [linux-next PATCH] mlx5: wrong page mask if CONFIG_ARCH_DMA_ADDR_T

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Date:	Sun, 12 Apr 2015 15:04:16 +0000
From:	Eli Cohen <eli@...lanox.com>
To:	Honggang Li <honli@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [linux-next PATCH] mlx5: wrong page mask if
 CONFIG_ARCH_DMA_ADDR_T_64BIT enabled for 32Bit architectures

Good catch, thanks!

There are more places in this file where PAGE_MASK is wrongly used. Need to fix them as well.

Also, see below [Eli]



-----Original Message-----
From: Honggang Li [mailto:honli@...hat.com] 
Sent: Sunday, April 12, 2015 2:06 PM
To: Eli Cohen; netdev@...r.kernel.org; linux-rdma@...r.kernel.org; linux-kernel@...r.kernel.org
Cc: Honggang Li
Subject: [linux-next PATCH] mlx5: wrong page mask if CONFIG_ARCH_DMA_ADDR_T_64BIT enabled for 32Bit architectures

If CONFIG_ARCH_DMA_ADDR_T_64BIT enabled for x86 systems and physical memory is more than 4GB, dma_map_page may return a valid memory address which greater than 0xffffffff. As a result, the mlx5 device page allocator RB tree will be initialized with valid addresses greater than 0xfffffff.

However, (addr & PAGE_MASK) set the high four bytes to zeros. So, it's impossible for the function, free_4k, to release the pages whose addresses greater than 4GB. Memory leaks. And mlx5_ib module can't release the pages when user try to remove the module, as a result, system hang.

[root@...a05 root]# dmesg  | grep addr | head
addr             = 3fe384000
addr & PAGE_MASK =  fe384000
[root@...a05 root]# rmmod mlx5_ib   <---- hang on

---------------------- cosnole log ----------------- mlx5_ib 0000:04:00.0: irq 138 for MSI/MSI-X
  alloc irq_desc for 139 on node -1
  alloc kstat_irqs on node -1
mlx5_ib 0000:04:00.0: irq 139 for MSI/MSI-X 0000:04:00.0:free_4k:221:(pid 1519): page not found 0000:04:00.0:free_4k:221:(pid 1519): page not found 0000:04:00.0:free_4k:221:(pid 1519): page not found 0000:04:00.0:free_4k:221:(pid 1519): page not found
---------------------- cosnole log -----------------

Signed-off-by: Honggang Li <honli@...hat.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c b/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
index df22383..27c72da 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
@@ -211,12 +211,14 @@ static int alloc_4k(struct mlx5_core_dev *dev, u64 *addr)
 	return 0;
 }
 
+#define MLX5_U64_4K_PAGE_MASK ((~(u64)0U) << PAGE_SHIFT)
+
 static void free_4k(struct mlx5_core_dev *dev, u64 addr)  {
 	struct fw_page *fwp;
 	int n;
 
-	fwp = find_fw_page(dev, addr & PAGE_MASK);
+	fwp = find_fw_page(dev, addr & MLX5_U64_4K_PAGE_MASK);
 	if (!fwp) {
 		mlx5_core_warn(dev, "page not found\n");
 		return;
@@ -241,7 +243,7 @@ static void free_4k(struct mlx5_core_dev *dev, u64 addr)  static int alloc_system_page(struct mlx5_core_dev *dev, u16 func_id)  {
 	struct page *page;
-	u64 addr;
+	u64 addr = 0; [Eli] Why is this required?
 	int err;
 	int nid = dev_to_node(&dev->pdev->dev);
 
--
1.8.3.1

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