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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?sQhFY+9YF1W1+Gp8+47YjHy9xot2y36SvmuADYYCasuknF/sG/ztaiWLQqMt?= =?us-ascii?Q?XI+BW73wAAo6LTUkwo554waqG94wX3B4mriQhYk05NMn4thX6G5RanSfPjkD?= =?us-ascii?Q?7gD5jqhfBhiAz9UUholF2tkXCwjjYanFDiyGzoXIS1L/t2P3fxg7Q09qeSSa?= =?us-ascii?Q?MAF3hRTgvZYFTceTbJYks0UzIOVCIcvEfTyNVzKBa43vCD6q7tVU1gWJ3+is?= =?us-ascii?Q?JuSo/UM1u3MxpMx7S3QlyhKpe/DxChJtm32wsadmm0wEi+QSHdMh7bTGunxq?= =?us-ascii?Q?7AwoHw5orw9KZni6a7zVakr6BNQ6l+b5j8ftgQfi/OYCj6qdO+xW+Un8SmKn?= =?us-ascii?Q?hSxl5qErGs1xTbnBm7AUkXumtYCJFaiTHOM6J3ks2gMf8ZlEb0WGIZhT49Qx?= =?us-ascii?Q?ql/VDncm/4XfDQCYiwwmRfRtekJzOtF3AT3QDmvZK0jKL0v0cFzYRcRdCdjO?= =?us-ascii?Q?CJmAGygjm2Q3Tx0pqd25zl8Le2uNKMHjr70F9UFVxNPx9ncxuwiQI9/BFj16?= =?us-ascii?Q?IraV88u2Tou8OOeKCczERNNSpytfD2CPkcbgLoEi9K1y3tSJapOrjE6jaPjx?= =?us-ascii?Q?97DRS0P+G63jlloh60SkI/B4JB9/fn9wnFk349B5++nT0BNl78wR88gbCDKQ?= =?us-ascii?Q?SxdppNJlMcgUAFr9xe+bSr17NaOcIMdCMfpnCx9dPHqSFN1lL9HTheBzZHAM?= =?us-ascii?Q?ORa6HXg0dcjaSCzUDTYVC4ERD8wDBZBXUOVAaJOEuaB19heiIzGHo682Eevb?= =?us-ascii?Q?Zm8M9wjLwg3i4I7DD9huW2TUjfVp2qWaLlHVnp0xJwBKt1IL2ZXEq74OZcHg?= =?us-ascii?Q?y2QeFlYAcP1kmpmEV58oetzBFBea8SaXQU9fkrgsZ9fv0sKab6Jm5HTt0NSU?= =?us-ascii?Q?kym8Qz8m9pa8Nckmg5dVfYZfYPgBkOHa5Muk9DkzK8BaK8RGeEdYnNEZZdN6?= =?us-ascii?Q?0RaKvHk4RDbyxAQIZPc8uBN2NlacsXh2oWc9V454+JaHfA8x82fpChgzTMrw?= =?us-ascii?Q?fikW7BZrtyUgGT9QdfBEDVLQ4W1tqdCKBP3FZ2VdLB5cflToLsTckvZAzQgu?= =?us-ascii?Q?AN0PEfnyi3Pzpm7zaFYyRxoYzx2Uz2jgYmbmkHOlTCVC6r6HwRjC7KuDz866?= =?us-ascii?Q?8490r/v7LD6BAzrAW0Ttmj5IyGMclrp4h3XgLwuLYIG/UnmsiGYLvm948uLt?= =?us-ascii?Q?2zAsbOLFOk4lv2oOTmLzPAv4rOk0SlBKaDSGDwspo3kfGvR90zDRpTFNsLEa?= =?us-ascii?Q?rz9FXNP0CPnB/Ar+yVKxiiWpvlk0RugTd5CMPx/a6Xh4UO8H3CLqaQksJP7d?= =?us-ascii?Q?eUG/Htd3e+Oy6S19hjpwn9uoRAYNVkCwmKoudjkeSww5aLJZU3rTPuDLT3rZ?= =?us-ascii?Q?RiTzRrr7ztoTG3MrHXHk4foy8PY2DbXNg+7AWhKjhJkw+gK8AzvCkoPqX0PL?= =?us-ascii?Q?lCXwkrZ4HcRTXhBFEqVjG3HMFtrXCSoI/QOwCbbmQHTJhYVvSMUh7ZkkH7YQ?= =?us-ascii?Q?rl4pS2wnjXC5bW3VwGyLPvHaZHS1vseb8cXyG/CxpBLjws7r5N/TeiU9bHrP?= =?us-ascii?Q?vVjuqU3wB/ny8qfVvFqBq6cjpmgYz3e60W6v1RzLi60QzttQXiYLkZdNDYRB?= =?us-ascii?Q?7iTZrqnEHZHmBf7I4Ksuz2EF/dR1P/+aTad3oXcXfsnQQjJIe9fSPY/O4Mmp?= =?us-ascii?Q?PsU5eDgcKE/H/k+MPbtH+W8V1hNIounZI9qkGeFSyNajf8aw?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 8242e47d-767f-4942-d624-08defc6a0702 X-MS-Exchange-CrossTenant-AuthSource: SA3PR12MB7901.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Aug 2026 14:15:45.0183 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 9N/yffcQ6zvVhOcuNkWqhxSqhJI0VRHtDg/fZLXgn/Hrm2qDS1tI9RN+IrOZMXtX4yVwuMrKq/sWXYBrzjJCvw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH8PR12MB9838 On Sat, Aug 15, 2026 at 03:51:02PM +0800, Dong Chenchen wrote: > When the forward output route cannot be used in icmp_route_lookup(), > it enters the "reverse path" and calls ip_route_input() on fl4_dec.daddr, > the original packet's source address. > > ip_route_input() only returns an error for truly invalid packets. For > unreachable addresses it will succeed and return an input route whose > dst.output is set to ip_rt_bug(). The existing check only rejects > RTN_LOCAL routes, so the RTN_UNREACHABLE route types can still be returned > and later used for output, syzkaller triggering a WARN_ON_ONCE() > in ip_rt_bug() as bellow: > > ------------[ cut here ]------------ > WARNING: net/ipv4/route.c:1273 at ip_rt_bug+0x14/0x20 > RIP: 0010:ip_rt_bug+0x14/0x20 > Call Trace: > ip_push_pending_frames+0xfa/0x100 > __icmp_send+0x905/0xf10 > ip_options_compile+0xc0/0xd0 > ip_rcv_finish_core+0x321/0xae0 > ip_rcv+0x1de/0x260 > __netif_receive_skb_one_core+0x11a/0x130 > netif_receive_skb+0x7b/0x260 > tun_get_user+0x11bf/0x1c10 > ------------[ cut here ]------------ > > Reject any input route that is RTN_UNREACHABLE to fix it. > > Fixes: 8b7817f3a959 ("[IPSEC]: Add ICMP host relookup support") > Signed-off-by: Dong Chenchen FYI, there's a new policy regarding AI review: " Patch authors are expected to proactively look into the AI-generated reviews and handle such feedback as any other kind of review: either debate it or address it. In both cases a reply on the mailing list is expected. " https://docs.kernel.org/next/process/maintainer-netdev.html#review-timelines > --- > net/ipv4/icmp.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c > index 0caedfc7ca92..4703d8dd6b47 100644 > --- a/net/ipv4/icmp.c > +++ b/net/ipv4/icmp.c > @@ -585,11 +585,11 @@ static struct rtable *icmp_route_lookup(struct net *net, struct flowi4 *fl4, > * checked fl4_dec.saddr above). However, a race condition > * may occur if the address is added to the interface > * concurrently. In that case, ip_route_input() returns a > - * LOCAL route with dst.output=ip_rt_bug, which must not > - * be used for output. > + * LOCAL or UNREACHABLE route with dst.output=ip_rt_bug, > + * which must not be used for output. > */ Why would the addition of an address lead to RTN_UNREACHABLE? This seems to be true for RTN_LOCAL, but not for RTN_UNREACHABLE. Similarly, it doesn't seem like RTN_UNREACHABLE is the result of a race condition. The comment needs to be reworded to reflect that. > - if (!err && rt2 && rt2->rt_type == RTN_LOCAL) { > - net_warn_ratelimited("detected local route for %pI4 during ICMP sending, src %pI4\n", > + if (!err && rt2 && (rt2->rt_type == RTN_LOCAL || rt2->rt_type == RTN_UNREACHABLE)) { > + net_warn_ratelimited("detected unusable input route for %pI4 during ICMP sending, src %pI4\n", > &fl4_dec.daddr, &fl4_dec.saddr); The check is fine, but if RTN_UNREACHABLE is not the result of a race condition, then net_warn_ratelimited() should only be emitted for RTN_LOCAL. > dst_release(&rt2->dst); > err = -EINVAL; > -- > 2.25.1 >