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AJvYcCWTb6RxUrO29dDs1/TgZqxdODz0FFuRjaO/Ae7lWwCXQxvYNFIymT/dY5brbD8qNStO0YCjhmA=@vger.kernel.org X-Gm-Message-State: AOJu0YxhLHQgrHgcRTpQFXYTJKSbWftPEcoARvnTqJDSKeGx98OhZHEv GTQbHg6aU6bET60Ba4kiH1SuE5iK40zsSuUVilj65LH71prvwdTxcrnHUtHneFUQL8Pmgf8TEb9 xvBNsXtFuSpUGu9jRXiOIzZfv95VHJ24= X-Gm-Gg: ATEYQzy1itMZjprSpmzZpqvO2idB60Riqzon3D0AguWZsysyj/XBSHzvAZ9rnQYrwdW YnCSDbeEh8cIJ26M+EgJ0NG/n1aayvHIqCRP7pL8acOHWWV9HomGEekjRfR2MY5eZLz1LQoTom7 cDfiReDvzLyV5i/IKnsPUi2Ob0NCcJb5eHlHfD93UoUkH61QQPGy7bLJ3L0Qhlv6lYu5gquBGtL rz2bYgkS+I32hCxReP++2A2iyw1q4chE0gjMQUBQgj2vIMsdLAtlw4b/Ol9k4iqUTB13Tm5hYtR FSD+Dw== X-Received: by 2002:a05:6820:8606:b0:67c:3021:908a with SMTP id 006d021491bc7-67dff554099mr1428783eaf.3.1774502492272; Wed, 25 Mar 2026 22:21:32 -0700 (PDT) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20260322040704.991766-3-weibunny.kernel@gmail.com> <20260323182357.177116-1-horms@kernel.org> In-Reply-To: <20260323182357.177116-1-horms@kernel.org> From: Wei Wang Date: Wed, 25 Mar 2026 22:21:21 -0700 X-Gm-Features: AQROBzAPAts7nlO-5nUR3MUgPplOCpprOuUPeza8FrUo6x72y1HZ16AvL-4WA14 Message-ID: Subject: Re: [PATCH v7 net-next 2/5] psp: add new netlink cmd for dev-assoc and dev-disassoc To: Simon Horman Cc: edumazet@google.com, willemdebruijn.kernel@gmail.com, netdev@vger.kernel.org, weibunny@fb.com, daniel.zahka@gmail.com, bobbyeshleman@meta.com, kuba@kernel.org, davem@davemloft.net, dw@davidwei.uk, andrew+netdev@lunn.ch Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Mar 23, 2026 at 11:24=E2=80=AFAM Simon Horman wr= ote: > > This is an AI-generated review of your patch. The human sending this > email has considered the AI review valid, or at least plausible. > > For local reproduction steps see https://netdev-ai.bots.linux.dev/ai-loca= l.html > --- > psp: add new netlink cmd for dev-assoc and dev-disassoc > > This commit adds new netlink commands (PSP_CMD_DEV_ASSOC and > PSP_CMD_DEV_DISASSOC) to associate non-PSP-capable devices (e.g. veth or > netkit) with a PSP device, enabling them to act as PSP-capable devices by > performing PSP encryption/decryption on the real PSP device. > > > diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c > > index 82de78a1d6bd..178b848989f1 100644 > > --- a/net/psp/psp_main.c > > +++ b/net/psp/psp_main.c > > @@ -37,8 +37,18 @@ struct mutex psp_devs_lock; > > */ > > int psp_dev_check_access(struct psp_dev *psd, struct net *net, bool ad= min) > > { > > + struct psp_assoc_dev *entry; > > + > > if (dev_net(psd->main_netdev) =3D=3D net) > > return 0; > > + > > + if (!admin) { > > + list_for_each_entry(entry, &psd->assoc_dev_list, dev_list= ) { > > + if (dev_net(entry->assoc_dev) =3D=3D net) > > + return 0; > > + } > > + } > > + > > return -ENOENT; > > } > > Does this list iteration have a race with psp_dev_unregister()? > > The new list_for_each_entry iteration over psd->assoc_dev_list in > psp_dev_check_access is called from psp_assoc_device_get_locked > (net/psp/psp_nl.c:615) without holding psd->lock. > > That caller obtains psd via psp_dev_get_for_sock which takes a refcount > but does not acquire psd->lock before calling psp_dev_check_access(psd, > ..., false). Since admin is false, the new code path is entered. > > Concurrently, psp_dev_unregister holds psd->lock and performs list_del + > kfree on the same assoc_dev_list entries: > > net/psp/psp_main.c:psp_dev_unregister() { > ... > list_for_each_entry_safe(entry, entry_tmp, &psd->assoc_dev_list, > dev_list) { > list_del(&entry->dev_list); > rcu_assign_pointer(entry->assoc_dev->psp_dev, NULL); > netdev_put(entry->assoc_dev, &entry->dev_tracker); > kfree(entry); > } > ... > } > > The list iterator in psp_dev_check_access can follow a next pointer into > freed memory, causing a use-after-free. > > Other callers (psp_device_get_and_lock, psp_nl_dev_get_dumpit, > psp_nl_get_stats_dumpit) correctly hold psd->lock before calling this > function, so the race is specific to the psp_assoc_device_get_locked path= . > Grabbing psd->lock before psp_dev_check_access () in the next versions. > > diff --git a/net/psp/psp_nl.c b/net/psp/psp_nl.c > > index b988f35412df..aa60a8277829 100644 > > --- a/net/psp/psp_nl.c > > +++ b/net/psp/psp_nl.c > > [ ... ] > > > @@ -291,6 +446,140 @@ int psp_nl_key_rotate_doit(struct sk_buff *skb, s= truct genl_info *info) > > return err; > > } > > > > +int psp_nl_dev_assoc_doit(struct sk_buff *skb, struct genl_info *info) > > +{ > > + struct psp_dev *psd =3D info->user_ptr[0]; > > + struct psp_assoc_dev *psp_assoc_dev; > > + struct net_device *assoc_dev; > > + u32 assoc_ifindex; > > + struct sk_buff *rsp; > > + struct net *net; > > + int nsid; > > + > > + if (GENL_REQ_ATTR_CHECK(info, PSP_A_DEV_IFINDEX)) > > + return -EINVAL; > > + > > + if (info->attrs[PSP_A_DEV_NSID]) { > > + nsid =3D nla_get_s32(info->attrs[PSP_A_DEV_NSID]); > > + > > + net =3D get_net_ns_by_id(genl_info_net(info), nsid); > > + if (!net) { > > + NL_SET_BAD_ATTR(info->extack, > > + info->attrs[PSP_A_DEV_NSID]); > > + return -EINVAL; > > + } > > + } else { > > + net =3D get_net(genl_info_net(info)); > > + } > > + > > + psp_assoc_dev =3D kzalloc(sizeof(*psp_assoc_dev), GFP_KERNEL); > > + if (!psp_assoc_dev) { > > + put_net(net); > > + return -ENOMEM; > > + } > > + > > + assoc_ifindex =3D nla_get_u32(info->attrs[PSP_A_DEV_IFINDEX]); > > + assoc_dev =3D netdev_get_by_index(net, assoc_ifindex, > > + &psp_assoc_dev->dev_tracker, > > + GFP_KERNEL); > > + if (!assoc_dev) { > > + put_net(net); > > + kfree(psp_assoc_dev); > > + NL_SET_BAD_ATTR(info->extack, info->attrs[PSP_A_DEV_IFIND= EX]); > > + return -ENODEV; > > + } > > + > > + /* Check if device is already associated with a PSP device */ > > + if (rcu_access_pointer(assoc_dev->psp_dev)) { > > + NL_SET_ERR_MSG(info->extack, > > + "Device already associated with a PSP devi= ce"); > > + netdev_put(assoc_dev, &psp_assoc_dev->dev_tracker); > > + put_net(net); > > + kfree(psp_assoc_dev); > > + return -EBUSY; > > + } > > + > > + psp_assoc_dev->assoc_dev =3D assoc_dev; > > + rsp =3D psp_nl_reply_new(info); > > + if (!rsp) { > > + netdev_put(assoc_dev, &psp_assoc_dev->dev_tracker); > > + put_net(net); > > + kfree(psp_assoc_dev); > > + return -ENOMEM; > > + } > > + > > + rcu_assign_pointer(assoc_dev->psp_dev, psd); > > + list_add_tail(&psp_assoc_dev->dev_list, &psd->assoc_dev_list); > > Can two concurrent PSP_CMD_DEV_ASSOC operations for the same net_device b= ut > different PSP devices both succeed? > > The function checks rcu_access_pointer(assoc_dev->psp_dev) to verify the > target net_device is not already associated with a PSP device, then later > writes rcu_assign_pointer(assoc_dev->psp_dev, psd) and adds the wrapper t= o > psd->assoc_dev_list. > > These operations are only serialized by psd->lock, which is a per-PSP-dev= ice > mutex acquired by the pre_doit callback psp_device_get_locked(). With > parallel_ops=3Dtrue in the psp_nl_family (net/psp/psp-nl-gen.c:165), two > concurrent PSP_CMD_DEV_ASSOC operations targeting different PSP devices > (each holding their own distinct psd->lock) but specifying the same targe= t > ifindex can both pass the rcu_access_pointer() NULL check. > > Both then call rcu_assign_pointer(assoc_dev->psp_dev, psd) and > list_add_tail(), resulting in the same net_device being added to two > different PSP devices' assoc_dev_list. The second rcu_assign_pointer > silently overwrites the first. > > This leaves the first PSP device's assoc_dev_list containing an entry who= se > net_device->psp_dev points to the wrong PSP device: > > Thread A (PSP device psd_A) Thread B (PSP device psd_B) > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > mutex_lock(&psd_A->lock) mutex_lock(&psd_B->lock) > rcu_access_pointer(dev->psp_dev) > -> NULL, proceed rcu_access_pointer(dev->psp_dev) > -> NULL, proceed > rcu_assign_pointer(dev->psp_dev, rcu_assign_pointer(dev->psp_dev, > psd_A) psd_B) > list_add_tail(entry_A, list_add_tail(entry_B, > &psd_A->list) &psd_B->list) > > A subsequent disassociation from the first PSP device would find its stal= e > psp_assoc_dev entry, call rcu_assign_pointer(found->assoc_dev->psp_dev, > NULL), and clear the pointer that now belongs to the second PSP device, > corrupting cross-device state. > > The data path check in psp_validate_xmit > (rcu_access_pointer(dev->psp_dev) =3D=3D pas->psd) can then fail incorrec= tly. Changing to use cmpxchg() on assoc_dev->psp_dev in the next version.