UBUNTU-CVE-2021-47131
In the Linux kernel, the following vulnerability has been resolved: net/tls: Fix use-after-free after the TLS device goes down and up When a netdev with active TLS offload goes down, tls_device_down is called to stop the offload and tear down the TLS context. However, the socket stays alive, and it still points to the TLS context, which is now deallocated. If a netdev goes up, while the connection is still active, and the data flow resumes after a number of TCP retransmissions, it will lead to a use-after-free of the TLS context. This commit addresses this bug by keeping the context alive until its normal destruction, and implements the necessary fallbacks, so that the connection can resume in software (non-offloaded) kTLS mode. On the TX side tls_sw_fallback is used to encrypt all packets. The RX side already has all the necessary fallbacks, because receiving non-decrypted packets is supported. The thing needed on the RX side is to block resync requests, which are normally produced after receiving non-decrypted packets. The necessary synchronization is implemented for a graceful teardown: first the fallbacks are deployed, then the driver resources are released (it used to be possible to have a tls_dev_resync after tls_dev_del). A new flag called TLS_RX_DEV_DEGRADED is added to indicate the fallback mode. It's used to skip the RX resync logic completely, as it becomes useless, and some objects may be released (for example, resync_async, which is allocated and freed by the driver).
02 / AFFECTED SOFTWARE
Affected packages
50 explicit affected versions
6 explicit affected versions
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62 explicit affected versions
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89 explicit affected versions
35 explicit affected versions
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91 explicit affected versions
13 explicit affected versions
4 explicit affected versions
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1 explicit affected versions
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16 explicit affected versions
10 explicit affected versions
46 explicit affected versions
7 explicit affected versions
12 explicit affected versions
12 explicit affected versions
1 explicit affected versions
7 explicit affected versions
79 explicit affected versions
12 explicit affected versions
94 explicit affected versions
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12 explicit affected versions
90 explicit affected versions
10 explicit affected versions
37 explicit affected versions
10 explicit affected versions
1 explicit affected versions
32 explicit affected versions
26 explicit affected versions
13 explicit affected versions
29 explicit affected versions
82 explicit affected versions
13 explicit affected versions
78 explicit affected versions
94 explicit affected versions
33 explicit affected versions
23 explicit affected versions
10 explicit affected versions
11 explicit affected versions
12 explicit affected versions
7 explicit affected versions
12 explicit affected versions
93 explicit affected versions
10 explicit affected versions
26 explicit affected versions
28 explicit affected versions
13 explicit affected versions
52 explicit affected versions
16 explicit affected versions
3 explicit affected versions
1 explicit affected versions
59 explicit affected versions
51 explicit affected versions
12 explicit affected versions
27 explicit affected versions
1 explicit affected versions
8 explicit affected versions
5 explicit affected versions
8 explicit affected versions
1 explicit affected versions
10 explicit affected versions
82 explicit affected versions
13 explicit affected versions
46 explicit affected versions
7 explicit affected versions
10 explicit affected versions
12 explicit affected versions
81 explicit affected versions
44 explicit affected versions
16 explicit affected versions
3 explicit affected versions
13 explicit affected versions
26 explicit affected versions
37 explicit affected versions
38 explicit affected versions
9 explicit affected versions
11 explicit affected versions
7 explicit affected versions
53 explicit affected versions
4 explicit affected versions
43 explicit affected versions
47 explicit affected versions
10 explicit affected versions
8 explicit affected versions
14 explicit affected versions
82 explicit affected versions
4 explicit affected versions
71 explicit affected versions
1 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: net/tls: Fix use-after-free after the TLS device goes down and up When a netdev with active TLS offload goes down, tls_device_down is called to stop the offload and tear down the TLS context. However, the socket stays alive, and it still points to the TLS context, which is now deallocated. If a netdev goes up, while the connection is still active, and the data flow resumes after a number of TCP retransmissions, it will lead to a use-after-free of the TLS context. This commit addresses this bug by keeping the context alive until its normal destruction, and implements the necessary fallbacks, so that the connection can resume in software (non-offloaded) kTLS mode. On the TX side tls_sw_fallback is used to encrypt all packets. The RX side already has all the necessary fallbacks, because receiving non-decrypted packets is supported. The thing needed on the RX side is to block resync requests, which are normally produced after receiving non-decrypted packets. The necessary synchronization is implemented for a graceful teardown: first the fallbacks are deployed, then the driver resources are released (it used to be possible to have a tls_dev_resync after tls_dev_del). A new flag called TLS_RX_DEV_DEGRADED is added to indicate the fallback mode. It's used to skip the RX resync logic completely, as it becomes useless, and some objects may be released (for example, resync_async, which is allocated and freed by the driver).
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/c55dcdd435aa6c6ad6ccac0a4c636d010ee367a4
- https://git.kernel.org/stable/c/0f1e6fe66977a864fe850522316f713d7b926fd9
- https://git.kernel.org/stable/c/c55dcdd435aa6c6ad6ccac0a4c636d010ee367a4
- https://git.kernel.org/stable/c/f1d4184f128dede82a59a841658ed40d4e6d3aa2
- https://ubuntu.com/security/CVE-2021-47131
- https://ubuntu.com/security/notices/USN-6924-1
- https://ubuntu.com/security/notices/USN-6924-2
- https://ubuntu.com/security/notices/USN-6953-1
- https://ubuntu.com/security/notices/USN-6979-1
- https://www.cve.org/CVERecord?id=CVE-2021-47131