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

[Petr Pavlu <petr.pavlu@suse.com>]

On 7/31/26 4:21 PM, Petr Pavlu wrote:
> 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@vger.kernel.org
>> Signed-off-by: Jiacheng Yu <yujiacheng3@huawei.com>
> 
> Looks ok to me.
> 
> Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
> 
> I'll give others more time to comment. If there are no further concerns,
> I plan to take this on modules-fixes.

I've queued the fix on modules-next for v7.3-rc1.

-- 
Thanks,
Petr