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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, zzzccc427@gmail.com Subject: [PATCH v2] xfrm: cache the offload ifindex for netlink dumps Date: Sat, 27 Jun 2026 11:50:58 +0800 Message-Id: <20260627035058.2745055-1-zzzccc427@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit copy_to_user_state_extra() only holds a reference to the outer xfrm_state. That does not pin x->xso.dev. NETDEV_DOWN and NETDEV_UNREGISTER can race through xfrm_dev_state_flush(), xfrm_state_delete(), and xfrm_dev_state_free(), which clears xso->dev and drops the netdev reference before the GETSA dump reaches xso_to_xuo() and reads xso->dev->ifindex. The buggy scenario involves two paths, with each column showing the order within that path: XFRM_MSG_GETSA dump path: NETDEV teardown path: 1. xfrm_get_sa() gets xfrm_state 1. xfrm_dev_state_flush() finds x 2. copy_to_user_state_extra() sees 2. xfrm_state_delete() removes x x->xso.dev from the SAD 3. copy_user_offload() calls 3. xfrm_dev_state_free() clears xso_to_xuo() xso->dev 4. xso->dev->ifindex dereferences 4. netdev_put() drops the device a detached net_device reference Avoid following the live net_device from the dump paths. Cache the attached ifindex in xfrm_dev_offload when state or policy offload is bound to a device, and serialize that snapshot instead. This preserves the user-visible XFRMA_OFFLOAD_DEV value without depending on the embedded net_device lifetime. Validation reproduced this kernel report: Oops: general protection fault Call Trace: copy_to_user_state_extra+0xb8d/0x1370 [xfrm_user] ? __pfx_copy_to_user_state_extra+0x10/0x10 [xfrm_user] ? __asan_memset+0x23/0x50 ? srso_alias_return_thunk+0x5/0xfbef5 ? __alloc_skb+0x342/0x960 ? srso_alias_return_thunk+0x5/0xfbef5 ? __asan_memset+0x23/0x50 ? srso_alias_return_thunk+0x5/0xfbef5 ? __nlmsg_put+0x147/0x1b0 dump_one_state+0x1c7/0x3e0 [xfrm_user] xfrm_state_netlink+0xcb/0x130 [xfrm_user] ? __pfx_xfrm_state_netlink+0x10/0x10 [xfrm_user] ? srso_alias_return_thunk+0x5/0xfbef5 ? xfrm_user_state_lookup.constprop.0+0x230/0x310 [xfrm_user] xfrm_get_sa+0x102/0x250 [xfrm_user] ? __pfx_xfrm_get_sa+0x10/0x10 [xfrm_user] xfrm_user_rcv_msg+0x504/0xaa0 [xfrm_user] ? __pfx_xfrm_user_rcv_msg+0x10/0x10 [xfrm_user] ? srso_alias_return_thunk+0x5/0xfbef5 ? stack_trace_save+0x8e/0xc0 ? __pfx_stack_trace_save+0x10/0x10 netlink_rcv_skb+0x11f/0x350 ? __pfx_xfrm_user_rcv_msg+0x10/0x10 [xfrm_user] ? __pfx_netlink_rcv_skb+0x10/0x10 ? __pfx_mutex_lock+0x10/0x10 ? srso_alias_return_thunk+0x5/0xfbef5 xfrm_netlink_rcv+0x65/0x80 [xfrm_user] netlink_unicast+0x600/0x870 ? __pfx_netlink_unicast+0x10/0x10 ? srso_alias_return_thunk+0x5/0xfbef5 ? __pfx_stack_trace_save+0x10/0x10 netlink_sendmsg+0x75d/0xc10 ? __pfx_netlink_sendmsg+0x10/0x10 ? srso_alias_return_thunk+0x5/0xfbef5 ____sys_sendmsg+0x77a/0x900 ? srso_alias_return_thunk+0x5/0xfbef5 ? __pfx_____sys_sendmsg+0x10/0x10 ? __pfx_copy_msghdr_from_user+0x10/0x10 ? release_sock+0x1a/0x1d0 ? srso_alias_return_thunk+0x5/0xfbef5 ? netlink_insert+0x143/0xec0 ___sys_sendmsg+0xff/0x180 ? __pfx____sys_sendmsg+0x10/0x10 ? _raw_spin_lock_irqsave+0x85/0xe0 ? do_getsockname+0xf9/0x170 ? srso_alias_return_thunk+0x5/0xfbef5 ? fdget+0x53/0x3b0 __sys_sendmsg+0x111/0x1a0 ? __pfx___sys_sendmsg+0x10/0x10 ? srso_alias_return_thunk+0x5/0xfbef5 ? __sys_getsockname+0x8c/0x100 do_syscall_64+0x102/0x5a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: 07b87f9eea0c ("xfrm: Fix unregister netdevice hang on hardware offload.") Assisted-by: Codex:gpt-5.5 Signed-off-by: Cen Zhang --- include/net/xfrm.h | 2 ++ net/xfrm/xfrm_device.c | 1 + net/xfrm/xfrm_state.c | 1 + net/xfrm/xfrm_user.c | 38 +++++++++++++++++++++++++++++--------- 4 files changed, 33 insertions(+), 9 deletions(-) diff --git a/include/net/xfrm.h b/include/net/xfrm.h index 519a0156a05c..a6d69aaa6cd2 100644 --- a/include/net/xfrm.h +++ b/include/net/xfrm.h @@ -162,6 +162,8 @@ struct xfrm_dev_offload { */ struct net_device *real_dev; unsigned long offload_handle; + /* Snapshot the attached device index for dump paths. */ + int ifindex; u8 dir : 2; u8 type : 2; u8 flags : 2; diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c index 630f3dd31cc5..44bfaa04e621 100644 --- a/net/xfrm/xfrm_device.c +++ b/net/xfrm/xfrm_device.c @@ -313,6 +313,7 @@ int xfrm_dev_state_add(struct net *net, struct xfrm_state *x, } xso->dev = dev; + xso->ifindex = dev->ifindex; netdev_tracker_alloc(dev, &xso->dev_tracker, GFP_ATOMIC); if (xuo->flags & XFRM_OFFLOAD_INBOUND) diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index c58cd024e3c6..707e29c82020 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -1547,6 +1547,7 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr, xso->type = XFRM_DEV_OFFLOAD_PACKET; xso->dir = xdo->dir; xso->dev = dev; + xso->ifindex = dev->ifindex; xso->flags = XFRM_DEV_OFFLOAD_FLAG_ACQ; netdev_hold(dev, &xso->dev_tracker, GFP_ATOMIC); error = dev->xfrmdev_ops->xdo_dev_state_add(dev, x, diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c index 6384795ee6b2..0eb87fc998d1 100644 --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -1201,17 +1201,26 @@ static int copy_sec_ctx(struct xfrm_sec_ctx *s, struct sk_buff *skb) return 0; } -static void xso_to_xuo(const struct xfrm_dev_offload *xso, - struct xfrm_user_offload *xuo) +static void xso_to_xuo_ifindex(const struct xfrm_dev_offload *xso, int ifindex, + struct xfrm_user_offload *xuo) { - xuo->ifindex = xso->dev->ifindex; + xuo->ifindex = ifindex; if (xso->dir == XFRM_DEV_OFFLOAD_IN) xuo->flags = XFRM_OFFLOAD_INBOUND; if (xso->type == XFRM_DEV_OFFLOAD_PACKET) xuo->flags |= XFRM_OFFLOAD_PACKET; } -static int copy_user_offload(struct xfrm_dev_offload *xso, struct sk_buff *skb) +#ifdef CONFIG_XFRM_MIGRATE +static void xso_to_xuo(const struct xfrm_dev_offload *xso, + struct xfrm_user_offload *xuo) +{ + xso_to_xuo_ifindex(xso, xso->dev->ifindex, xuo); +} +#endif + +static int copy_user_offload_ifindex(const struct xfrm_dev_offload *xso, + int ifindex, struct sk_buff *skb) { struct xfrm_user_offload *xuo; struct nlattr *attr; @@ -1222,11 +1231,22 @@ static int copy_user_offload(struct xfrm_dev_offload *xso, struct sk_buff *skb) xuo = nla_data(attr); memset(xuo, 0, sizeof(*xuo)); - xso_to_xuo(xso, xuo); + xso_to_xuo_ifindex(xso, ifindex, xuo); return 0; } +static int copy_user_offload(struct xfrm_dev_offload *xso, struct sk_buff *skb) +{ + return copy_user_offload_ifindex(xso, xso->dev->ifindex, skb); +} + +static int copy_user_state_offload(const struct xfrm_dev_offload *xso, + struct sk_buff *skb) +{ + return copy_user_offload_ifindex(xso, READ_ONCE(xso->ifindex), skb); +} + static bool xfrm_redact(void) { return IS_ENABLED(CONFIG_SECURITY) && @@ -1433,8 +1453,8 @@ static int copy_to_user_state_extra(struct xfrm_state *x, &x->replay); if (ret) goto out; - if(x->xso.dev) - ret = copy_user_offload(&x->xso, skb); + if (READ_ONCE(x->xso.dev)) + ret = copy_user_state_offload(&x->xso, skb); if (ret) goto out; if (x->if_id) { @@ -4046,8 +4066,8 @@ static inline unsigned int xfrm_sa_len(struct xfrm_state *x) l += nla_total_size(sizeof(*x->coaddr)); if (x->props.extra_flags) l += nla_total_size(sizeof(x->props.extra_flags)); - if (x->xso.dev) - l += nla_total_size(sizeof(struct xfrm_user_offload)); + if (READ_ONCE(x->xso.dev)) + l += nla_total_size(sizeof(struct xfrm_user_offload)); if (x->props.smark.v | x->props.smark.m) { l += nla_total_size(sizeof(x->props.smark.v)); l += nla_total_size(sizeof(x->props.smark.m)); -- 2.43.0