5.5

CVE-2021-47593

mptcp: clear 'kern' flag from fallback sockets

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

mptcp: clear 'kern' flag from fallback sockets

The mptcp ULP extension relies on sk->sk_sock_kern being set correctly:
It prevents setsockopt(fd, IPPROTO_TCP, TCP_ULP, "mptcp", 6); from
working for plain tcp sockets (any userspace-exposed socket).

But in case of fallback, accept() can return a plain tcp sk.
In such case, sk is still tagged as 'kernel' and setsockopt will work.

This will crash the kernel, The subflow extension has a NULL ctx->conn
mptcp socket:

BUG: KASAN: null-ptr-deref in subflow_data_ready+0x181/0x2b0
Call Trace:
 tcp_data_ready+0xf8/0x370
 [..]
Daten sind bereitgestellt durch National Vulnerability Database (NVD)
Linux ≫ Linux Kernel Version >= 5.6 < 5.10.88
Linux ≫ Linux Kernel Version >= 5.11 < 5.15.11
Linux ≫ Linux Kernel Version5.16 Updaterc1
Linux ≫ Linux Kernel Version5.16 Updaterc2
Linux ≫ Linux Kernel Version5.16 Updaterc3
Linux ≫ Linux Kernel Version5.16 Updaterc4
Linux ≫ Linux Kernel Version5.16 Updaterc5
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Zu dieser CVE wurde keine Warnung gefunden.
EPSS Metriken
Typ Quelle Score Percentile
EPSS FIRST.org 0.25% 0.156
CVSS Metriken
Quelle Base Score Exploit Score Impact Score Vector String
nvd@nist.gov 5.5 1.8 3.6
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE-476 NULL Pointer Dereference

The product dereferences a pointer that it expects to be valid but is NULL.

https://git.kernel.org/stable/c/451f1eded7f56e93aaf52eb547ba97742d9c0e97
Patch
https://git.kernel.org/stable/c/c26ac0ea3a91c210cf90452e625dc441adf3e549
Patch
https://git.kernel.org/stable/c/d6692b3b97bdc165d150f4c1505751a323a80717
Patch