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Fri, 13 Feb 2026 00:43:06 -0800 (PST) Received: from lima-ubuntu.hz.ali.com ([47.246.98.214]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-824c6a62c48sm1695723b3a.29.2026.02.13.00.43.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Feb 2026 00:43:06 -0800 (PST) From: Qing Wang To: Alexander Viro , Christian Brauner , Jan Kara , Pavel Tikhomirov , Bhavik Sachdev , Andrei Vagin Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Qing Wang , syzbot+9e03a9535ea65f687a44@syzkaller.appspotmail.com Subject: [PATCH] statmount: Fix the null-ptr-deref in do_statmount() Date: Fri, 13 Feb 2026 16:42:59 +0800 Message-Id: <20260213084259.2423971-1-wangqing7171@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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_OR_NULL(). Fixes: 0e5032237ee5 ("statmount: accept fd as a parameter") Reported-by: syzbot+9e03a9535ea65f687a44@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/698e287a.a70a0220.2c38d7.009e.GAE@googl= e.com/ Tested-by: syzbot+9e03a9535ea65f687a44@syzkaller.appspotmail.com Signed-off-by: Qing Wang --- fs/namespace.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index a67cbe42746d..d769d50de5d6 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -5678,13 +5678,15 @@ static int do_statmount(struct kstatmount *s, u64 m= nt_id, u64 mnt_ns_id, =20 s->mnt =3D mnt_file->f_path.mnt; ns =3D real_mount(s->mnt)->mnt_ns; - if (!ns) + if (IS_ERR_OR_NULL(ns)) { /* * We can't set mount point and mnt_ns_id since we don't have a * ns for the mount. This can happen if the mount is unmounted - * with MNT_DETACH. + * with MNT_DETACH or if it's an internal mount. */ s->mask &=3D ~(STATMOUNT_MNT_POINT | STATMOUNT_MNT_NS_ID); + ns =3D NULL; + } } else { /* Has the namespace already been emptied? */ if (mnt_ns_id && mnt_ns_empty(ns)) --=20 2.34.1