UBUNTU-CVE-2021-47506
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix use-after-free due to delegation race A delegation break could arrive as soon as we've called vfs_setlease. A delegation break runs a callback which immediately (in nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru. If we then exit nfs4_set_delegation without hashing the delegation, it will be freed as soon as the callback is done with it, without ever being removed from del_recall_lru. Symptoms show up later as use-after-free or list corruption warnings, usually in the laundromat thread. I suspect aba2072f4523 "nfsd: grant read delegations to clients holding writes" made this bug easier to hit, but I looked as far back as v3.0 and it looks to me it already had the same problem. So I'm not sure where the bug was introduced; it may have been there from the beginning.
02 / AFFECTED SOFTWARE
Affected packages
50 explicit affected versions
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31 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
34 explicit affected versions
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4 explicit affected versions
54 explicit affected versions
34 explicit affected versions
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1 explicit affected versions
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103 explicit affected versions
10 explicit affected versions
8 explicit affected versions
14 explicit affected versions
35 explicit affected versions
4 explicit affected versions
23 explicit affected versions
1 explicit affected versions
10 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix use-after-free due to delegation race A delegation break could arrive as soon as we've called vfs_setlease. A delegation break runs a callback which immediately (in nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru. If we then exit nfs4_set_delegation without hashing the delegation, it will be freed as soon as the callback is done with it, without ever being removed from del_recall_lru. Symptoms show up later as use-after-free or list corruption warnings, usually in the laundromat thread. I suspect aba2072f4523 "nfsd: grant read delegations to clients holding writes" made this bug easier to hit, but I looked as far back as v3.0 and it looks to me it already had the same problem. So I'm not sure where the bug was introduced; it may have been there from the beginning.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/548ec0805c399c65ed66c6641be467f717833ab5
- https://git.kernel.org/stable/c/04a8d07f3d58308b92630045560799a3faa3ebce
- https://git.kernel.org/stable/c/148c816f10fd11df27ca6a9b3238cdd42fa72cd3
- https://git.kernel.org/stable/c/2becaa990b93cbd2928292c0b669d3abb6cf06d4
- https://git.kernel.org/stable/c/33645d3e22720cac1e4548f8fef57bf0649536ee
- https://git.kernel.org/stable/c/348714018139c39533c55661a0c7c990671396b4
- https://git.kernel.org/stable/c/548ec0805c399c65ed66c6641be467f717833ab5
- https://git.kernel.org/stable/c/e0759696de6851d7536efddfdd2dfed4c4df1f09
- https://git.kernel.org/stable/c/eeb0711801f5e19ef654371b627682aed3b11373
- https://ubuntu.com/security/CVE-2021-47506
- https://ubuntu.com/security/notices/USN-7506-1
- https://ubuntu.com/security/notices/USN-7506-2
- https://ubuntu.com/security/notices/USN-7506-3
- https://ubuntu.com/security/notices/USN-7506-4
- https://www.cve.org/CVERecord?id=CVE-2021-47506