{
   "containers": {
      "cna": {
         "providerMetadata": {
            "orgId": "f4215fc3-5b6b-47ff-a258-f7189bd81038"
         },
         "descriptions": [
            {
               "lang": "en",
               "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: fix use-after-free in tw_timer_handler\n\nA real world panic issue was found as follow in Linux 5.4.\n\n    BUG: unable to handle page fault for address: ffffde49a863de28\n    PGD 7e6fe62067 P4D 7e6fe62067 PUD 7e6fe63067 PMD f51e064067 PTE 0\n    RIP: 0010:tw_timer_handler+0x20/0x40\n    Call Trace:\n     <IRQ>\n     call_timer_fn+0x2b/0x120\n     run_timer_softirq+0x1ef/0x450\n     __do_softirq+0x10d/0x2b8\n     irq_exit+0xc7/0xd0\n     smp_apic_timer_interrupt+0x68/0x120\n     apic_timer_interrupt+0xf/0x20\n\nThis issue was also reported since 2017 in the thread [1],\nunfortunately, the issue was still can be reproduced after fixing\nDCCP.\n\nThe ipv4_mib_exit_net is called before tcp_sk_exit_batch when a net\nnamespace is destroyed since tcp_sk_ops is registered befrore\nipv4_mib_ops, which means tcp_sk_ops is in the front of ipv4_mib_ops\nin the list of pernet_list. There will be a use-after-free on\nnet->mib.net_statistics in tw_timer_handler after ipv4_mib_exit_net\nif there are some inflight time-wait timers.\n\nThis bug is not introduced by commit f2bf415cfed7 (\"mib: add net to\nNET_ADD_STATS_BH\") since the net_statistics is a global variable\ninstead of dynamic allocation and freeing. Actually, commit\n61a7e26028b9 (\"mib: put net statistics on struct net\") introduces\nthe bug since it put net statistics on struct net and free it when\nnet namespace is destroyed.\n\nMoving init_ipv4_mibs() to the front of tcp_init() to fix this bug\nand replace pr_crit() with panic() since continuing is meaningless\nwhen init_ipv4_mibs() fails.\n\n[1] https://groups.google.com/g/syzkaller/c/p1tn-_Kc6l4/m/smuL_FMAAgAJ?pli=1"
            }
         ],
         "affected": [
            {
               "product": "Linux",
               "vendor": "Linux",
               "defaultStatus": "unaffected",
               "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
               "programFiles": [
                  "net/ipv4/af_inet.c"
               ],
               "versions": [
                  {
                     "version": "61a7e26028b9",
                     "lessThan": "15579e1301f8",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "61a7e26028b9",
                     "lessThan": "e73164e89d1b",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "61a7e26028b9",
                     "lessThan": "5c2fe20ad37f",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "61a7e26028b9",
                     "lessThan": "a8e1944b44f9",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "61a7e26028b9",
                     "lessThan": "fe5838c22b98",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "61a7e26028b9",
                     "lessThan": "2386e81a1d27",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "61a7e26028b9",
                     "lessThan": "08eacbd141e2",
                     "status": "affected",
                     "versionType": "git"
                  },
                  {
                     "version": "61a7e26028b9",
                     "lessThan": "e22e45fc9e41",
                     "status": "affected",
                     "versionType": "git"
                  }
               ]
            },
            {
               "product": "Linux",
               "vendor": "Linux",
               "defaultStatus": "affected",
               "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
               "programFiles": [
                  "net/ipv4/af_inet.c"
               ],
               "versions": [
                  {
                     "version": "2.6.27",
                     "status": "affected"
                  },
                  {
                     "version": "0",
                     "lessThan": "2.6.27",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "4.4.298",
                     "lessThanOrEqual": "4.4.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "4.9.296",
                     "lessThanOrEqual": "4.9.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "4.14.261",
                     "lessThanOrEqual": "4.14.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "4.19.224",
                     "lessThanOrEqual": "4.19.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "5.4.170",
                     "lessThanOrEqual": "5.4.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "5.10.90",
                     "lessThanOrEqual": "5.10.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "5.15.13",
                     "lessThanOrEqual": "5.15.*",
                     "status": "unaffected",
                     "versionType": "custom"
                  },
                  {
                     "version": "5.16",
                     "lessThanOrEqual": "*",
                     "status": "unaffected",
                     "versionType": "original_commit_for_fix"
                  }
               ]
            }
         ],
         "references": [
            {
               "url": "https://git.kernel.org/stable/c/15579e1301f856ad9385d720c9267c11032a5022"
            },
            {
               "url": "https://git.kernel.org/stable/c/e73164e89d1be561228a4534e1091369ee4ba41a"
            },
            {
               "url": "https://git.kernel.org/stable/c/5c2fe20ad37ff56070ae0acb34152333976929b4"
            },
            {
               "url": "https://git.kernel.org/stable/c/a8e1944b44f94f5c5f530e434c5eaee787254566"
            },
            {
               "url": "https://git.kernel.org/stable/c/fe5838c22b986c1190f1dce9aa09bf6a491c1a69"
            },
            {
               "url": "https://git.kernel.org/stable/c/2386e81a1d277f540e1285565c9d41d531bb69d4"
            },
            {
               "url": "https://git.kernel.org/stable/c/08eacbd141e2495d2fcdde84358a06c4f95cbb13"
            },
            {
               "url": "https://git.kernel.org/stable/c/e22e45fc9e41bf9fcc1e92cfb78eb92786728ef0"
            }
         ],
         "title": "net: fix use-after-free in tw_timer_handler",
         "x_generator": {
            "engine": "bippy-a5840b7849dd"
         }
      }
   },
   "cveMetadata": {
      "assignerOrgId": "f4215fc3-5b6b-47ff-a258-f7189bd81038",
      "cveID": "CVE-2021-46936",
      "requesterUserId": "gregkh@kernel.org",
      "serial": "1",
      "state": "PUBLISHED"
   },
   "dataType": "CVE_RECORD",
   "dataVersion": "5.0"
}