[PATCH] gianfar: synchronize DMA API usage by free_skb_rx_queue w/ gfar_new_page

From: Arseny Solokha
Date: Sun Jan 29 2017 - 08:02:38 EST

From: Arseny Solokha <asolokha@xxxxxxxxxx>

In spite of switching to paged allocation of Rx buffers, the driver still
called dma_unmap_single() in the Rx queues tear-down path.

The DMA region unmapping code in free_skb_rx_queue() basically predates
the introduction of paged allocation to the driver. While being refactored,
it apparently hasn't reflected the change in the DMA API usage by its
counterpart gfar_new_page().

As a result, setting an interface to the DOWN state now yields the following:

# ip link set eth2 down
fsl-gianfar ffe24000.ethernet: DMA-API: device driver frees DMA memory with wrong function [device address=0x000000001ecd0000] [size=40]
------------[ cut here ]------------
WARNING: CPU: 1 PID: 189 at lib/dma-debug.c:1123 check_unmap+0x8e0/0xa28
CPU: 1 PID: 189 Comm: ip Tainted: G O 4.9.5 #1
task: dee73400 task.stack: dede2000
NIP: c02101e8 LR: c02101e8 CTR: c0260d74
REGS: dede3bb0 TRAP: 0700 Tainted: G O (4.9.5)
MSR: 00021000 <CE,ME> CR: 28002222 XER: 00000000

GPR00: c02101e8 dede3c60 dee73400 000000b6 dfbd033c dfbd36c4 1f622000 dede2000
GPR08: 00000007 c05b1634 1f622000 00000000 22002484 100a9904 00000000 00000000
GPR16: 00000000 db4c849c 00000002 db4c8480 00000001 df142240 db4c84bc 00000000
GPR24: c0706148 c0700000 00029000 c07552e8 c07323b4 dede3cb8 c07605e0 db535540
NIP [c02101e8] check_unmap+0x8e0/0xa28
LR [c02101e8] check_unmap+0x8e0/0xa28
Call Trace:
[dede3c60] [c02101e8] check_unmap+0x8e0/0xa28 (unreliable)
[dede3cb0] [c02103b8] debug_dma_unmap_page+0x88/0x9c
[dede3d30] [c02dffbc] free_skb_resources+0x2c4/0x404
[dede3d80] [c02e39b4] gfar_close+0x24/0xc8
[dede3da0] [c0361550] __dev_close_many+0xa0/0xf8
[dede3dd0] [c03616f0] __dev_close+0x2c/0x4c
[dede3df0] [c036b1b8] __dev_change_flags+0xa0/0x174
[dede3e10] [c036b2ac] dev_change_flags+0x20/0x60
[dede3e30] [c03e130c] devinet_ioctl+0x540/0x824
[dede3e90] [c0347dcc] sock_ioctl+0x134/0x298
[dede3eb0] [c0111814] do_vfs_ioctl+0xac/0x854
[dede3f20] [c0111ffc] SyS_ioctl+0x40/0x74
[dede3f40] [c000f290] ret_from_syscall+0x0/0x3c
--- interrupt: c01 at 0xff45da0
LR = 0xff45cd0
Instruction dump:
811d001c 7c66482e 813d0020 9061000c 807f000c 5463103a 7cc6182e 3c60c052
386309ac 90c10008 4cc63182 4826b845 <0fe00000> 4bfffa60 3c80c052 388402c4
---[ end trace 695ae6d7ac1d0c47 ]---
Mapped at:
[<c02e22a8>] gfar_alloc_rx_buffs+0x178/0x248
[<c02e3ef0>] startup_gfar+0x368/0x570
[<c036aeb4>] __dev_open+0xdc/0x150
[<c036b1b8>] __dev_change_flags+0xa0/0x174
[<c036b2ac>] dev_change_flags+0x20/0x60

Even though the issue was discovered in 4.9 kernel, the code in question
is identical in the current net and net-next trees.

Fixes: 75354148ce69 ("gianfar: Add paged allocation and Rx S/G")
Signed-off-by: Arseny Solokha <asolokha@xxxxxxxxxx>
drivers/net/ethernet/freescale/gianfar.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index c1b671667920..957bfc220978 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -2010,8 +2010,8 @@ static void free_skb_rx_queue(struct gfar_priv_rx_q *rx_queue)
if (!rxb->page)

- dma_unmap_single(rx_queue->dev, rxb->dma,
+ dma_unmap_page(rx_queue->dev, rxb->dma,

rxb->page = NULL;