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[87.205.15.91]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6a3769d97b7sm365276a12.20.2026.08.12.01.17.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Aug 2026 01:17:13 -0700 (PDT) From: Krystian Kaniewski To: Jason Gunthorpe , Leon Romanovsky , linux-rdma@vger.kernel.org Cc: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Or Har-Toov , Paolo Abeni , Selvin Xavier , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, syzbot+5fe14f2ff4ccbace9a26@syzkaller.appspotmail.com Subject: [PATCH v4] RDMA/core: Reject unregistering netdevs in ib_get_eth_speed Date: Wed, 12 Aug 2026 10:16:41 +0200 Message-ID: <20260812081708.32468-1-krystianmkaniewski@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ib_device_get_netdev() intentionally returns a referenced net_device even when it is unregistering, so matching and cleanup callers can still find the association. The reference keeps struct net_device allocated, but does not guarantee that the device remains operational. ib_get_eth_speed() uses the returned device operationally by invoking its ethtool callback. Although that call is made under RTNL, the function does not verify the registration state first. An asynchronous RDMA port query can therefore call into a netdev after NETDEV_UNREGISTER and ndo_uninit have completed. Check for NETREG_REGISTERED while holding RTNL and return -ENODEV for a device which is being unregistered. Keeping RTNL across the check and the ethtool operation prevents unregister from starting between them. Keep the speed fallback and warning under RTNL as well, so the warning can safely read netdev->name. Drop the netdev reference before releasing RTNL once all accesses to the device are complete. Fixes: d41861942fc5 ("IB/core: Add generic function to extract IB speed from netdev") Reported-by: syzbot+5fe14f2ff4ccbace9a26@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=5fe14f2ff4ccbace9a26 Signed-off-by: Krystian Kaniewski --- v4: - Keep the speed fallback and warning under RTNL and use netdev->name directly, as suggested by Jason Gunthorpe. - Release the netdev reference before rtnl_unlock() on both paths. - Drop the [PATCH net] subject prefix because the patch targets RDMA. - Rebase onto the RDMA for-next branch. v3: https://lore.kernel.org/all/20260810133124.44513-1-krystianmkaniewski@gmail.com/ v2: https://lore.kernel.org/all/20260803121140.261329-1-krystianmkaniewski@gmail.com/ drivers/infiniband/core/verbs.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c index 367822efff36..b31d61513335 100644 --- a/drivers/infiniband/core/verbs.c +++ b/drivers/infiniband/core/verbs.c @@ -2058,11 +2058,13 @@ int ib_get_eth_speed(struct ib_device *dev, u32 port_num, u16 *speed, u8 *width) return -ENODEV; rtnl_lock(); - rc = __ethtool_get_link_ksettings(netdev, &lksettings); - rtnl_unlock(); - - dev_put(netdev); + if (READ_ONCE(netdev->reg_state) != NETREG_REGISTERED) { + dev_put(netdev); + rtnl_unlock(); + return -ENODEV; + } + rc = __ethtool_get_link_ksettings(netdev, &lksettings); if (!rc && lksettings.base.speed != (u32)SPEED_UNKNOWN) { netdev_speed = lksettings.base.speed; } else { @@ -2071,6 +2073,8 @@ int ib_get_eth_speed(struct ib_device *dev, u32 port_num, u16 *speed, u8 *width) pr_warn("%s speed is unknown, defaulting to %u\n", netdev->name, netdev_speed); } + dev_put(netdev); + rtnl_unlock(); ib_get_width_and_speed(netdev_speed, lksettings.lanes, speed, width); -- 2.53.0