ghsa-7fpf-q83q-74mx
Vulnerability from github
Published
2025-07-28 12:30
Modified
2025-07-28 12:30
Details

In the Linux kernel, the following vulnerability has been resolved:

rpl: Fix use-after-free in rpl_do_srh_inline().

Running lwt_dst_cache_ref_loop.sh in selftest with KASAN triggers the splat below [0].

rpl_do_srh_inline() fetches ipv6_hdr(skb) and accesses it after skb_cow_head(), which is illegal as the header could be freed then.

Let's fix it by making oldhdr to a local struct instead of a pointer.

[0]: [root@fedora net]# ./lwt_dst_cache_ref_loop.sh ... TEST: rpl (input) [ 57.631529] ================================================================== BUG: KASAN: slab-use-after-free in rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174) Read of size 40 at addr ffff888122bf96d8 by task ping6/1543

CPU: 50 UID: 0 PID: 1543 Comm: ping6 Not tainted 6.16.0-rc5-01302-gfadd1e6231b1 #23 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: dump_stack_lvl (lib/dump_stack.c:122) print_report (mm/kasan/report.c:409 mm/kasan/report.c:521) kasan_report (mm/kasan/report.c:221 mm/kasan/report.c:636) kasan_check_range (mm/kasan/generic.c:175 (discriminator 1) mm/kasan/generic.c:189 (discriminator 1)) __asan_memmove (mm/kasan/shadow.c:94 (discriminator 2)) rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174) rpl_input (net/ipv6/rpl_iptunnel.c:201 net/ipv6/rpl_iptunnel.c:282) lwtunnel_input (net/core/lwtunnel.c:459) ipv6_rcv (./include/net/dst.h:471 (discriminator 1) ./include/net/dst.h:469 (discriminator 1) net/ipv6/ip6_input.c:79 (discriminator 1) ./include/linux/netfilter.h:317 (discriminator 1) ./include/linux/netfilter.h:311 (discriminator 1) net/ipv6/ip6_input.c:311 (discriminator 1)) __netif_receive_skb_one_core (net/core/dev.c:5967) process_backlog (./include/linux/rcupdate.h:869 net/core/dev.c:6440) __napi_poll.constprop.0 (net/core/dev.c:7452) net_rx_action (net/core/dev.c:7518 net/core/dev.c:7643) handle_softirqs (kernel/softirq.c:579) do_softirq (kernel/softirq.c:480 (discriminator 20)) __local_bh_enable_ip (kernel/softirq.c:407) __dev_queue_xmit (net/core/dev.c:4740) ip6_finish_output2 (./include/linux/netdevice.h:3358 ./include/net/neighbour.h:526 ./include/net/neighbour.h:540 net/ipv6/ip6_output.c:141) ip6_finish_output (net/ipv6/ip6_output.c:215 net/ipv6/ip6_output.c:226) ip6_output (./include/linux/netfilter.h:306 net/ipv6/ip6_output.c:248) ip6_send_skb (net/ipv6/ip6_output.c:1983) rawv6_sendmsg (net/ipv6/raw.c:588 net/ipv6/raw.c:918) __sys_sendto (net/socket.c:714 (discriminator 1) net/socket.c:729 (discriminator 1) net/socket.c:2228 (discriminator 1)) __x64_sys_sendto (net/socket.c:2231) do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1)) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) RIP: 0033:0x7f68cffb2a06 Code: 5d e8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 75 19 83 e2 39 83 fa 08 75 11 e8 26 ff ff ff 66 0f 1f 44 00 00 48 8b 45 10 0f 05 <48> 8b 5d f8 c9 c3 0f 1f 40 00 f3 0f 1e fa 55 48 89 e5 48 83 ec 08 RSP: 002b:00007ffefb7c53d0 EFLAGS: 00000202 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 0000564cd69f10a0 RCX: 00007f68cffb2a06 RDX: 0000000000000040 RSI: 0000564cd69f10a4 RDI: 0000000000000003 RBP: 00007ffefb7c53f0 R08: 0000564cd6a032ac R09: 000000000000001c R10: 0000000000000000 R11: 0000000000000202 R12: 0000564cd69f10a4 R13: 0000000000000040 R14: 00007ffefb7c66e0 R15: 0000564cd69f10a0

Allocated by task 1543: kasan_save_stack (mm/kasan/common.c:48) kasan_save_track (mm/kasan/common.c:60 (discriminator 1) mm/kasan/common.c:69 (discriminator 1)) __kasan_slab_alloc (mm/kasan/common.c:319 mm/kasan/common.c:345) kmem_cache_alloc_node_noprof (./include/linux/kasan.h:250 mm/slub.c:4148 mm/slub.c:4197 mm/slub.c:4249) kmalloc_reserve (net/core/skbuff.c:581 (discriminator 88)) __alloc_skb (net/core/skbuff.c:669) __ip6_append_data (net/ipv6/ip6_output.c:1672 (discriminator 1)) ip6_ ---truncated---

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{
  "affected": [],
  "aliases": [
    "CVE-2025-38476"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-07-28T12:15:29Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nrpl: Fix use-after-free in rpl_do_srh_inline().\n\nRunning lwt_dst_cache_ref_loop.sh in selftest with KASAN triggers\nthe splat below [0].\n\nrpl_do_srh_inline() fetches ipv6_hdr(skb) and accesses it after\nskb_cow_head(), which is illegal as the header could be freed then.\n\nLet\u0027s fix it by making oldhdr to a local struct instead of a pointer.\n\n[0]:\n[root@fedora net]# ./lwt_dst_cache_ref_loop.sh\n...\nTEST: rpl (input)\n[   57.631529] ==================================================================\nBUG: KASAN: slab-use-after-free in rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174)\nRead of size 40 at addr ffff888122bf96d8 by task ping6/1543\n\nCPU: 50 UID: 0 PID: 1543 Comm: ping6 Not tainted 6.16.0-rc5-01302-gfadd1e6231b1 #23 PREEMPT(voluntary)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\nCall Trace:\n \u003cIRQ\u003e\n dump_stack_lvl (lib/dump_stack.c:122)\n print_report (mm/kasan/report.c:409 mm/kasan/report.c:521)\n kasan_report (mm/kasan/report.c:221 mm/kasan/report.c:636)\n kasan_check_range (mm/kasan/generic.c:175 (discriminator 1) mm/kasan/generic.c:189 (discriminator 1))\n __asan_memmove (mm/kasan/shadow.c:94 (discriminator 2))\n rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174)\n rpl_input (net/ipv6/rpl_iptunnel.c:201 net/ipv6/rpl_iptunnel.c:282)\n lwtunnel_input (net/core/lwtunnel.c:459)\n ipv6_rcv (./include/net/dst.h:471 (discriminator 1) ./include/net/dst.h:469 (discriminator 1) net/ipv6/ip6_input.c:79 (discriminator 1) ./include/linux/netfilter.h:317 (discriminator 1) ./include/linux/netfilter.h:311 (discriminator 1) net/ipv6/ip6_input.c:311 (discriminator 1))\n __netif_receive_skb_one_core (net/core/dev.c:5967)\n process_backlog (./include/linux/rcupdate.h:869 net/core/dev.c:6440)\n __napi_poll.constprop.0 (net/core/dev.c:7452)\n net_rx_action (net/core/dev.c:7518 net/core/dev.c:7643)\n handle_softirqs (kernel/softirq.c:579)\n do_softirq (kernel/softirq.c:480 (discriminator 20))\n \u003c/IRQ\u003e\n \u003cTASK\u003e\n __local_bh_enable_ip (kernel/softirq.c:407)\n __dev_queue_xmit (net/core/dev.c:4740)\n ip6_finish_output2 (./include/linux/netdevice.h:3358 ./include/net/neighbour.h:526 ./include/net/neighbour.h:540 net/ipv6/ip6_output.c:141)\n ip6_finish_output (net/ipv6/ip6_output.c:215 net/ipv6/ip6_output.c:226)\n ip6_output (./include/linux/netfilter.h:306 net/ipv6/ip6_output.c:248)\n ip6_send_skb (net/ipv6/ip6_output.c:1983)\n rawv6_sendmsg (net/ipv6/raw.c:588 net/ipv6/raw.c:918)\n __sys_sendto (net/socket.c:714 (discriminator 1) net/socket.c:729 (discriminator 1) net/socket.c:2228 (discriminator 1))\n __x64_sys_sendto (net/socket.c:2231)\n do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))\n entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\nRIP: 0033:0x7f68cffb2a06\nCode: 5d e8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 75 19 83 e2 39 83 fa 08 75 11 e8 26 ff ff ff 66 0f 1f 44 00 00 48 8b 45 10 0f 05 \u003c48\u003e 8b 5d f8 c9 c3 0f 1f 40 00 f3 0f 1e fa 55 48 89 e5 48 83 ec 08\nRSP: 002b:00007ffefb7c53d0 EFLAGS: 00000202 ORIG_RAX: 000000000000002c\nRAX: ffffffffffffffda RBX: 0000564cd69f10a0 RCX: 00007f68cffb2a06\nRDX: 0000000000000040 RSI: 0000564cd69f10a4 RDI: 0000000000000003\nRBP: 00007ffefb7c53f0 R08: 0000564cd6a032ac R09: 000000000000001c\nR10: 0000000000000000 R11: 0000000000000202 R12: 0000564cd69f10a4\nR13: 0000000000000040 R14: 00007ffefb7c66e0 R15: 0000564cd69f10a0\n \u003c/TASK\u003e\n\nAllocated by task 1543:\n kasan_save_stack (mm/kasan/common.c:48)\n kasan_save_track (mm/kasan/common.c:60 (discriminator 1) mm/kasan/common.c:69 (discriminator 1))\n __kasan_slab_alloc (mm/kasan/common.c:319 mm/kasan/common.c:345)\n kmem_cache_alloc_node_noprof (./include/linux/kasan.h:250 mm/slub.c:4148 mm/slub.c:4197 mm/slub.c:4249)\n kmalloc_reserve (net/core/skbuff.c:581 (discriminator 88))\n __alloc_skb (net/core/skbuff.c:669)\n __ip6_append_data (net/ipv6/ip6_output.c:1672 (discriminator 1))\n ip6_\n---truncated---",
  "id": "GHSA-7fpf-q83q-74mx",
  "modified": "2025-07-28T12:30:35Z",
  "published": "2025-07-28T12:30:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38476"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/034b428aa3583373a5a20b1c5931bb2b3cae1f36"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/06ec83b6c792fde1f710c1de3e836da6e257c4c4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/62dcd9d6e61c39122d2f251a26829e2e55b0a11d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b640daa2822a39ff76e70200cb2b7b892b896dce"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e8101506ab86dd78f823b7028f2036a380f3a12a"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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