CVSS3
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
AI Score
Confidence
High
EPSS
Percentile
5.1%
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.
OS | Version | Architecture | Package | Version | Filename |
---|---|---|---|---|---|
ubuntu | 18.04 | noarch | linux | < any | UNKNOWN |
ubuntu | 20.04 | noarch | linux | < 5.4.0-105.119 | UNKNOWN |
ubuntu | 18.04 | noarch | linux-aws | < any | UNKNOWN |
ubuntu | 20.04 | noarch | linux-aws | < 5.4.0-1069.73 | UNKNOWN |
ubuntu | 18.04 | noarch | linux-aws-5.4 | < any | UNKNOWN |
ubuntu | 16.04 | noarch | linux-aws-hwe | < 4.15.0-1124.133~16.04.1 | UNKNOWN |
ubuntu | 20.04 | noarch | linux-azure | < 5.4.0-1073.76 | UNKNOWN |
ubuntu | 14.04 | noarch | linux-azure | < 4.15.0-1134.147~14.04.1 | UNKNOWN |
ubuntu | 16.04 | noarch | linux-azure | < 4.15.0-1134.147~16.04.1 | UNKNOWN |
ubuntu | 18.04 | noarch | linux-azure-4.15 | < any | UNKNOWN |
git.kernel.org/linus/5ec7d18d1813a5bead0b495045606c93873aecbb (5.16-rc8)
git.kernel.org/stable/c/5ec7d18d1813a5bead0b495045606c93873aecbb
git.kernel.org/stable/c/75799e71df1da11394740b43ae5686646179561d
git.kernel.org/stable/c/769d14abd35e0e153b5149c3e1e989a9d719e3ff
git.kernel.org/stable/c/831de271452b87657fcf8d715ee20519b79caef5
git.kernel.org/stable/c/8873140f95d4977bf37e4cf0d5c5e3f6e34cdd3e
git.kernel.org/stable/c/af6e6e58f7ebf86b4e7201694b1e4f3a62cbc3ec
launchpad.net/bugs/cve/CVE-2021-46929
nvd.nist.gov/vuln/detail/CVE-2021-46929
security-tracker.debian.org/tracker/CVE-2021-46929
www.cve.org/CVERecord?id=CVE-2021-46929