ath10k: Avoid potential page alloc BUG_ON in tx free path

[Kalle Valo]

Mohammed Shafi Shajakhan <mohammed at qti.qualcomm.com> wrote:
> From: Mohammed Shafi Shajakhan <mohammed at qti.qualcomm.com>
> 
> 'ath10k_htt_tx_free_cont_txbuf' and 'ath10k_htt_tx_free_cont_frag_desc'
> have NULL pointer checks to avoid crash if they are called twice
> but this is as of now not sufficient as these pointers are not assigned
> to NULL once the contiguous DMA memory allocation is freed, fix this.
> Though this may not be hit with the explicity check of state variable
> 'tx_mem_allocated' check, good to have this addressed as well.
> 
> Below BUG_ON is hit when the above scenario is simulated
> with kernel debugging enabled
> 
>  page:f6d09a00 count:0 mapcount:-127 mapping:  (null)
> index:0x0
>  flags: 0x40000000()
>  page dumped because: VM_BUG_ON_PAGE(page_ref_count(page)
> == 0)
>  ------------[ cut here ]------------
>  kernel BUG at ./include/linux/mm.h:445!
>  invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC
>  EIP is at put_page_testzero.part.88+0xd/0xf
>  Call Trace:
>   [<c118a2cc>] __free_pages+0x3c/0x40
>   [<c118a30e>] free_pages+0x3e/0x50
>   [<c10222b4>] dma_generic_free_coherent+0x24/0x30
>   [<f8c1d9a8>] ath10k_htt_tx_free_cont_txbuf+0xf8/0x140
> 
>   [<f8c1e2a9>] ath10k_htt_tx_destroy+0x29/0xa0
> 
>   [<f8c143e0>] ath10k_core_destroy+0x60/0x80 [ath10k_core]
>   [<f8acd7e9>] ath10k_pci_remove+0x79/0xa0 [ath10k_pci]
>   [<c13ed7a8>] pci_device_remove+0x38/0xb0
>   [<c14d3492>] __device_release_driver+0x72/0x100
>   [<c14d36b7>] driver_detach+0x97/0xa0
>   [<c14d29c0>] bus_remove_driver+0x40/0x80
>   [<c14d427a>] driver_unregister+0x2a/0x60
>   [<c13ec768>] pci_unregister_driver+0x18/0x70
>   [<f8aced4f>] ath10k_pci_exit+0xd/0x2be [ath10k_pci]
>   [<c1101e78>] SyS_delete_module+0x158/0x210
>   [<c11b34f1>] ? __might_fault+0x41/0xa0
>   [<c11b353b>] ? __might_fault+0x8b/0xa0
>   [<c1001a4b>] do_fast_syscall_32+0x9b/0x1c0
>   [<c178da34>] sysenter_past_esp+0x45/0x74
> 
> Signed-off-by: Mohammed Shafi Shajakhan <mohammed at qti.qualcomm.com>

Patch applied to ath-next branch of ath.git, thanks.

02a9e08d7374 ath10k: Avoid potential page alloc BUG_ON in tx free path

-- 
https://patchwork.kernel.org/patch/9463923/

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