Re: [PATCH v2] params: fix charp corruption on allocation failure

[Petr Pavlu]

On 7/29/26 2:32 PM, Jiacheng Yu wrote:
> param_set_charp() stores charp parameters in allocated memory after slab is
> available, and releases the previous value when the parameter is updated.
> 
> The previous value is released before the replacement allocation succeeds.
> If kmalloc_parameter() fails, the setter returns -ENOMEM with the parameter
> left as NULL.
> 
> Failing zswap's compressor update before zswap is initialized can later
> trigger:
> 
>   BUG: kernel NULL pointer dereference, address: 0000000000000000
>   RIP: 0010:strcmp+0x10/0x30
>   Call Trace:
>     zswap_setup+0x3b1/0x490
>     zswap_enabled_param_set+0x5b/0xa0
>     param_attr_store+0x93/0xe0
>     module_attr_store+0x1c/0x30
>     kernfs_fop_write_iter+0x116/0x1f0
> 
> Allocate and copy the replacement first, then replace the parameter value
> only after allocation succeeds.
> 
> Fixes: e180a6b7759a ("param: fix charp parameters set via sysfs")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jiacheng Yu <yujiacheng3@xxxxxxxxxx>

Looks ok to me.

Reviewed-by: Petr Pavlu <petr.pavlu@xxxxxxxx>

I'll give others more time to comment. If there are no further concerns,
I plan to take this on modules-fixes.

-- 
Thanks,
Petr