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: [email protected]
> Signed-off-by: Jiacheng Yu <[email protected]>
Looks ok to me.
Reviewed-by: Petr Pavlu <[email protected]>
I'll give others more time to comment. If there are no further concerns,
I plan to take this on modules-fixes.
--
Thanks,
Petr
