Re: [PATCH v3] statmount: Fix the null-ptr-deref in do_statmount()

[Bhavik Sachdev]

On Fri Feb 13, 2026 at 4:00 PM IST, Qing Wang wrote:
> If the mount is internal, it's mnt_ns will be MNT_NS_INTERNAL, which is
> defined as ERR_PTR(-EINVAL). So, in the do_statmount(), need to check ns
> of mount by IS_ERR() and return.
>
> Fixes: 0e5032237ee5 ("statmount: accept fd as a parameter")
> Reported-by: syzbot+9e03a9535ea65f687a44@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://lore.kernel.org/all/698e287a.a70a0220.2c38d7.009e.GAE@xxxxxxxxxx/
> Signed-off-by: Qing Wang <wangqing7171@xxxxxxxxx>
> ---
>  fs/namespace.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index a67cbe42746d..90700df65f0d 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -5678,6 +5678,8 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id,
>  
>  		s->mnt = mnt_file->f_path.mnt;
>  		ns = real_mount(s->mnt)->mnt_ns;
> +		if (IS_ERR(ns))
> +			return PTR_ERR(ns);
>  		if (!ns)
>  			/*
>  			 * We can't set mount point and mnt_ns_id since we don't have a

Looks good to me.

Reviewed-by: Bhavik Sachdev <b.sachdev1904@xxxxxxxxx>