CVE-2021-46929 (GCVE-0-2021-46929)
Vulnerability from cvelistv5
Published
2024-02-27 09:43
Modified
2025-05-04 07:00
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: sctp: use call_rcu to free endpoint This patch is to delay the endpoint free by calling call_rcu() to fix another use-after-free issue in sctp_sock_dump(): BUG: KASAN: use-after-free in __lock_acquire+0x36d9/0x4c20 Call Trace: __lock_acquire+0x36d9/0x4c20 kernel/locking/lockdep.c:3218 lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168 spin_lock_bh include/linux/spinlock.h:334 [inline] __lock_sock+0x203/0x350 net/core/sock.c:2253 lock_sock_nested+0xfe/0x120 net/core/sock.c:2774 lock_sock include/net/sock.h:1492 [inline] sctp_sock_dump+0x122/0xb20 net/sctp/diag.c:324 sctp_for_each_transport+0x2b5/0x370 net/sctp/socket.c:5091 sctp_diag_dump+0x3ac/0x660 net/sctp/diag.c:527 __inet_diag_dump+0xa8/0x140 net/ipv4/inet_diag.c:1049 inet_diag_dump+0x9b/0x110 net/ipv4/inet_diag.c:1065 netlink_dump+0x606/0x1080 net/netlink/af_netlink.c:2244 __netlink_dump_start+0x59a/0x7c0 net/netlink/af_netlink.c:2352 netlink_dump_start include/linux/netlink.h:216 [inline] inet_diag_handler_cmd+0x2ce/0x3f0 net/ipv4/inet_diag.c:1170 __sock_diag_cmd net/core/sock_diag.c:232 [inline] sock_diag_rcv_msg+0x31d/0x410 net/core/sock_diag.c:263 netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2477 sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:274 This issue occurs when asoc is peeled off and the old sk is freed after getting it by asoc->base.sk and before calling lock_sock(sk). To prevent the sk free, as a holder of the sk, ep should be alive when calling lock_sock(). This patch uses call_rcu() and moves sock_put and ep free into sctp_endpoint_destroy_rcu(), so that it's safe to try to hold the ep under rcu_read_lock in sctp_transport_traverse_process(). If sctp_endpoint_hold() returns true, it means this ep is still alive and we have held it and can continue to dump it; If it returns false, it means this ep is dead and can be freed after rcu_read_unlock, and we should skip it. In sctp_sock_dump(), after locking the sk, if this ep is different from tsp->asoc->ep, it means during this dumping, this asoc was peeled off before calling lock_sock(), and the sk should be skipped; If this ep is the same with tsp->asoc->ep, it means no peeloff happens on this asoc, and due to lock_sock, no peeloff will happen either until release_sock. Note that delaying endpoint free won't delay the port release, as the port release happens in sctp_endpoint_destroy() before calling call_rcu(). Also, freeing endpoint by call_rcu() makes it safe to access the sk by asoc->base.sk in sctp_assocs_seq_show() and sctp_rcv(). Thanks Jones to bring this issue up. v1->v2: - improve the changelog. - add kfree(ep) into sctp_endpoint_destroy_rcu(), as Jakub noticed.
References
Impacted products
Vendor Product Version
Linux Linux Version: d25adbeb0cdb860fb39e09cdd025e9cfc954c5ab
Version: d25adbeb0cdb860fb39e09cdd025e9cfc954c5ab
Version: d25adbeb0cdb860fb39e09cdd025e9cfc954c5ab
Version: d25adbeb0cdb860fb39e09cdd025e9cfc954c5ab
Version: d25adbeb0cdb860fb39e09cdd025e9cfc954c5ab
Version: d25adbeb0cdb860fb39e09cdd025e9cfc954c5ab
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\"include/net/sctp/structs.h\", \"net/sctp/diag.c\", \"net/sctp/endpointola.c\", \"net/sctp/socket.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/8873140f95d4977bf37e4cf0d5c5e3f6e34cdd3e\"}, {\"url\": \"https://git.kernel.org/stable/c/af6e6e58f7ebf86b4e7201694b1e4f3a62cbc3ec\"}, {\"url\": \"https://git.kernel.org/stable/c/831de271452b87657fcf8d715ee20519b79caef5\"}, {\"url\": \"https://git.kernel.org/stable/c/769d14abd35e0e153b5149c3e1e989a9d719e3ff\"}, {\"url\": \"https://git.kernel.org/stable/c/75799e71df1da11394740b43ae5686646179561d\"}, {\"url\": \"https://git.kernel.org/stable/c/5ec7d18d1813a5bead0b495045606c93873aecbb\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nsctp: use call_rcu to free endpoint\\n\\nThis patch is to delay the endpoint free by calling call_rcu() to fix\\nanother use-after-free issue in sctp_sock_dump():\\n\\n  BUG: KASAN: use-after-free in __lock_acquire+0x36d9/0x4c20\\n  Call Trace:\\n    __lock_acquire+0x36d9/0x4c20 kernel/locking/lockdep.c:3218\\n    lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844\\n    __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]\\n    _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168\\n    spin_lock_bh include/linux/spinlock.h:334 [inline]\\n    __lock_sock+0x203/0x350 net/core/sock.c:2253\\n    lock_sock_nested+0xfe/0x120 net/core/sock.c:2774\\n    lock_sock include/net/sock.h:1492 [inline]\\n    sctp_sock_dump+0x122/0xb20 net/sctp/diag.c:324\\n    sctp_for_each_transport+0x2b5/0x370 net/sctp/socket.c:5091\\n    sctp_diag_dump+0x3ac/0x660 net/sctp/diag.c:527\\n    __inet_diag_dump+0xa8/0x140 net/ipv4/inet_diag.c:1049\\n    inet_diag_dump+0x9b/0x110 net/ipv4/inet_diag.c:1065\\n    netlink_dump+0x606/0x1080 net/netlink/af_netlink.c:2244\\n    __netlink_dump_start+0x59a/0x7c0 net/netlink/af_netlink.c:2352\\n    netlink_dump_start include/linux/netlink.h:216 [inline]\\n    inet_diag_handler_cmd+0x2ce/0x3f0 net/ipv4/inet_diag.c:1170\\n    __sock_diag_cmd net/core/sock_diag.c:232 [inline]\\n    sock_diag_rcv_msg+0x31d/0x410 net/core/sock_diag.c:263\\n    netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2477\\n    sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:274\\n\\nThis issue occurs when asoc is peeled off and the old sk is freed after\\ngetting it by asoc-\u003ebase.sk and before calling lock_sock(sk).\\n\\nTo prevent the sk free, as a holder of the sk, ep should be alive when\\ncalling lock_sock(). This patch uses call_rcu() and moves sock_put and\\nep free into sctp_endpoint_destroy_rcu(), so that it\u0027s safe to try to\\nhold the ep under rcu_read_lock in sctp_transport_traverse_process().\\n\\nIf sctp_endpoint_hold() returns true, it means this ep is still alive\\nand we have held it and can continue to dump it; If it returns false,\\nit means this ep is dead and can be freed after rcu_read_unlock, and\\nwe should skip it.\\n\\nIn sctp_sock_dump(), after locking the sk, if this ep is different from\\ntsp-\u003easoc-\u003eep, it means during this dumping, this asoc was peeled off\\nbefore calling lock_sock(), and the sk should be skipped; If this ep is\\nthe same with tsp-\u003easoc-\u003eep, it means no peeloff happens on this asoc,\\nand due to lock_sock, no peeloff will happen either until release_sock.\\n\\nNote that delaying endpoint free won\u0027t delay the port release, as the\\nport release happens in sctp_endpoint_destroy() before calling call_rcu().\\nAlso, freeing endpoint by call_rcu() makes it safe to access the sk by\\nasoc-\u003ebase.sk in sctp_assocs_seq_show() and sctp_rcv().\\n\\nThanks Jones to bring this issue up.\\n\\nv1-\u003ev2:\\n  - improve the changelog.\\n  - add kfree(ep) into sctp_endpoint_destroy_rcu(), as Jakub noticed.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.14.261\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.19.224\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.170\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.90\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.13\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.16\", \"versionStartIncluding\": \"4.14\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2025-05-04T07:00:32.322Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-46929\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2025-05-04T07:00:32.322Z\", \"dateReserved\": \"2024-02-25T13:45:52.720Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-02-27T09:43:58.047Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}


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