Date:	Fri, 20 Feb 2015 17:20:40 +0200
From:	Kalle Valo <kvalo@....qualcomm.com>
To:	Josh Cartwright <joshc@...com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"John W. Linville" <linville@...driver.com>,
	<linux-wireless@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>,
	Jason Liu <r64343@...escale.com>
Subject: Re: [PATCH -stable] ath6kl: fix struct hif_scatter_req list handling

Josh Cartwright <joshc@...com> writes:

> From: Kalle Valo <kvalo@....qualcomm.com>
>
> commit 31b9cc9a873dcab161999622314f98a75d838975 upstream.
>
> Jason noticed that with Yocto GCC 4.8.1 ath6kl crashes with this iperf command:
>
> iperf -c $TARGET_IP -i 5 -t 50 -w 1M
>
> The crash was:
>
> Unable to handle kernel paging request at virtual address 1a480000
> pgd = 80004000
> [1a480000] *pgd=00000000
> Internal error: Oops: 805 [#1] SMP ARM
> Modules linked in: ath6kl_sdio ath6kl_core [last unloaded: ath6kl_core]
> CPU: 0 PID: 1953 Comm: kworker/u4:0 Not tainted 3.10.9-1.0.0_alpha+dbf364b #1
> Workqueue: ath6kl ath6kl_sdio_write_async_work [ath6kl_sdio]
> task: dcc9a680 ti: dc9ae000 task.ti: dc9ae000
> PC is at v7_dma_clean_range+0x20/0x38
> LR is at dma_cache_maint_page+0x50/0x54
> pc : [<8001a6f8>]    lr : [<800170fc>]    psr: 20000093
> sp : dc9afcf8  ip : 8001a748  fp : 00000004
> r10: 00000000  r9 : 00000001  r8 : 00000000
> r7 : 00000001  r6 : 00000000  r5 : 80cb7000  r4 : 03f9a480
> r3 : 0000001f  r2 : 00000020  r1 : 1a480000  r0 : 1a480000
> Flags: nzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
> Control: 10c53c7d  Table: 6cc5004a  DAC: 00000015
> Process kworker/u4:0 (pid: 1953, stack limit = 0xdc9ae238)
> Stack: (0xdc9afcf8 to 0xdc9b0000)
> fce0:                                                       80c9b29c 00000000
> fd00: 00000000 80017134 8001a748 dc302ac0 00000000 00000000 dc454a00 80c12ed8
> fd20: dc115410 80017238 00000000 dc454a10 00000001 80017588 00000001 00000000
> fd40: 00000000 dc302ac0 dc9afe38 dc9afe68 00000004 80c12ed8 00000000 dc454a00
> fd60: 00000004 80436f88 00000000 00000000 00000600 0000ffff 0000000c 80c113c4
> fd80: 80c9b29c 00000001 00000004 dc115470 60000013 dc302ac0 dc46e000 dc302800
> fda0: dc9afe10 dc302b78 60000013 dc302ac0 dc46e000 00000035 dc46e5b0 80438c90
> fdc0: dc9afe10 dc302800 dc302800 dc9afe68 dc9afe38 80424cb4 00000005 dc9afe10
> fde0: dc9afe20 80424de8 dc9afe10 dc302800 dc46e910 80424e90 dc473c00 dc454f00
> fe00: 000001b5 7f619d64 dcc7c830 00000000 00000000 dc9afe38 dc9afe68 00000000
> fe20: 00000000 00000000 dc9afe28 dc9afe28 80424d80 00000000 00000035 9cac0034
> fe40: 00000000 00000000 00000000 00000000 000001b5 00000000 00000000 00000000
> fe60: dc9afe68 dc9afe10 3b9aca00 00000000 00000080 00000034 00000000 00000100
> fe80: 00000000 00000000 dc9afe10 00000004 dc454a00 00000000 dc46e010 dc46e96c
> fea0: dc46e000 dc46e964 00200200 00100100 dc46e910 7f619ec0 00000600 80c0e770
> fec0: dc15a900 dcc7c838 00000000 dc46e954 8042d434 dcc44680 dc46e954 dc004400
> fee0: dc454500 00000000 00000000 dc9ae038 dc004400 8003c450 dcc44680 dc004414
> ff00: dc46e954 dc454500 00000001 dcc44680 dc004414 dcc44698 dc9ae000 dc9ae030
> ff20: 00000001 dc9ae000 dc004400 8003d158 8003d020 00000000 00000000 80c53941
> ff40: dc9aff64 dcb71ea0 00000000 dcc44680 8003d020 00000000 00000000 00000000
> ff60: 00000000 80042480 00000000 00000000 000000f8 dcc44680 00000000 00000000
> ff80: dc9aff80 dc9aff80 00000000 00000000 dc9aff90 dc9aff90 dc9affac dcb71ea0
> ffa0: 800423cc 00000000 00000000 8000e018 00000000 00000000 00000000 00000000
> ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> ffe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
> [<8001a6f8>] (v7_dma_clean_range+0x20/0x38) from [<800170fc>] (dma_cache_maint_page+0x50/0x54)
> [<800170fc>] (dma_cache_maint_page+0x50/0x54) from [<80017134>] (__dma_page_cpu_to_dev+0x34/0x9c)
> [<80017134>] (__dma_page_cpu_to_dev+0x34/0x9c) from [<80017238>] (arm_dma_map_page+0x64/0x68)
> [<80017238>] (arm_dma_map_page+0x64/0x68) from [<80017588>] (arm_dma_map_sg+0x7c/0xf4)
> [<80017588>] (arm_dma_map_sg+0x7c/0xf4) from [<80436f88>] (sdhci_send_command+0x894/0xe00)
> [<80436f88>] (sdhci_send_command+0x894/0xe00) from [<80438c90>] (sdhci_request+0xc0/0x1ec)
> [<80438c90>] (sdhci_request+0xc0/0x1ec) from [<80424cb4>] (mmc_start_request+0xb8/0xd4)
> [<80424cb4>] (mmc_start_request+0xb8/0xd4) from [<80424de8>] (__mmc_start_req+0x60/0x84)
> [<80424de8>] (__mmc_start_req+0x60/0x84) from [<80424e90>] (mmc_wait_for_req+0x10/0x20)
> [<80424e90>] (mmc_wait_for_req+0x10/0x20) from [<7f619d64>] (ath6kl_sdio_scat_rw.isra.10+0x1dc/0x240 [ath6kl_sdio])
> [<7f619d64>] (ath6kl_sdio_scat_rw.isra.10+0x1dc/0x240 [ath6kl_sdio]) from [<7f619ec0>] (ath6kl_sdio_write_async_work+0x5c/0x104 [ath6kl_sdio])
> [<7f619ec0>] (ath6kl_sdio_write_async_work+0x5c/0x104 [ath6kl_sdio]) from [<8003c450>] (process_one_work+0x10c/0x370)
> [<8003c450>] (process_one_work+0x10c/0x370) from [<8003d158>] (worker_thread+0x138/0x3fc)
> [<8003d158>] (worker_thread+0x138/0x3fc) from [<80042480>] (kthread+0xb4/0xb8)
> [<80042480>] (kthread+0xb4/0xb8) from [<8000e018>] (ret_from_fork+0x14/0x3c)
> Code: e1a02312 e2423001 e1c00003 f57ff04f (ee070f3a)
> ---[ end trace 0c038f0b8e0b67a3 ]---
> Kernel panic - not syncing: Fatal exception
>
> Jason's analysis:
>
>   "The GCC 4.8.1 compiler will not do the for-loop till scat_entries, instead,
>    it only run one round loop. This may be caused by that the GCC 4.8.1 thought
>    that the scat_list only have one item and then no need to do full iteration,
>    but this is simply wrong by looking at the assebly code. This will cause the sg
>    buffer not get set when scat_entries > 1 and thus lead to kernel panic.
>
>    Note: This issue not observed with GCC 4.7.2, only found on the GCC 4.8.1)"
>
> Fix this by using the normal [0] style for defining unknown number of list
> entries following the struct. This also fixes corruption with scat_q_depth, which
> was mistankely added to the end of struct and overwritten if there were more
> than item in the scat list.
>
> Reported-by: Jason Liu <r64343@...escale.com>
> Tested-by: Jason Liu <r64343@...escale.com>
> Signed-off-by: Kalle Valo <kvalo@....qualcomm.com>
> ---
> We ran into this issue in the 3.14.y stable tree which has been fixed upstream
> since 3.16.  Please consider pulling it back to 3.14.y at least;  it may be
> relevant further back, but it isn't clear when the issue first cropped up.  I'm
> hoping Kalle can comment.

I agree, it would be good to get this to stable.

-- 
Kalle Valo
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