Re: [PATCH v3] mwifiex: fix sleep in atomic context bugs caused by dev_coredumpv

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, May 23, 2022 at 01:28:10PM +0800, Duoming Zhou wrote:
> There are sleep in atomic context bugs when uploading device dump
> data in mwifiex. The root cause is that dev_coredumpv could not
> be used in atomic contexts, because it calls dev_set_name which
> include operations that may sleep. The call tree shows execution
> paths that could lead to bugs:
> 
>    (Interrupt context)
> fw_dump_timer_fn
>   mwifiex_upload_device_dump
>     dev_coredumpv(..., GFP_KERNEL)
>       dev_coredumpm()
>         kzalloc(sizeof(*devcd), gfp); //may sleep
>         dev_set_name
>           kobject_set_name_vargs
>             kvasprintf_const(GFP_KERNEL, ...); //may sleep
>             kstrdup(s, GFP_KERNEL); //may sleep
> 
> In order to let dev_coredumpv support atomic contexts, this patch
> changes the gfp_t parameter of kvasprintf_const and kstrdup in
> kobject_set_name_vargs from GFP_KERNEL to GFP_ATOMIC. What's more,
> In order to mitigate bug, this patch changes the gfp_t parameter
> of dev_coredumpv from GFP_KERNEL to GFP_ATOMIC.
> 
> Fixes: 57670ee882d4 ("mwifiex: device dump support via devcoredump framework")
> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
> ---
> Changes in v3:
>   - Let dev_coredumpv support atomic contexts.
> 
>  drivers/net/wireless/marvell/mwifiex/main.c | 2 +-
>  lib/kobject.c                               | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/marvell/mwifiex/main.c b/drivers/net/wireless/marvell/mwifiex/main.c
> index ace7371c477..258906920a2 100644
> --- a/drivers/net/wireless/marvell/mwifiex/main.c
> +++ b/drivers/net/wireless/marvell/mwifiex/main.c
> @@ -1116,7 +1116,7 @@ void mwifiex_upload_device_dump(struct mwifiex_adapter *adapter)
>  	mwifiex_dbg(adapter, MSG,
>  		    "== mwifiex dump information to /sys/class/devcoredump start\n");
>  	dev_coredumpv(adapter->dev, adapter->devdump_data, adapter->devdump_len,
> -		      GFP_KERNEL);
> +		      GFP_ATOMIC);
>  	mwifiex_dbg(adapter, MSG,
>  		    "== mwifiex dump information to /sys/class/devcoredump end\n");
>  
> diff --git a/lib/kobject.c b/lib/kobject.c
> index 5f0e71ab292..7672c54944c 100644
> --- a/lib/kobject.c
> +++ b/lib/kobject.c
> @@ -254,7 +254,7 @@ int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
>  	if (kobj->name && !fmt)
>  		return 0;
>  
> -	s = kvasprintf_const(GFP_KERNEL, fmt, vargs);
> +	s = kvasprintf_const(GFP_ATOMIC, fmt, vargs);
>  	if (!s)
>  		return -ENOMEM;
>  
> @@ -267,7 +267,7 @@ int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
>  	if (strchr(s, '/')) {
>  		char *t;
>  
> -		t = kstrdup(s, GFP_KERNEL);
> +		t = kstrdup(s, GFP_ATOMIC);
>  		kfree_const(s);
>  		if (!t)
>  			return -ENOMEM;

Please no, you are hurting the whole kernel because of one odd user.
Please do not make these calls under atomic context.

thanks,

greg k-h