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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.78%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.78% probability · 54th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-416
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/04a8d07f3d58308b92630045560799a3faa3ebcePatch
- https://git.kernel.org/stable/c/148c816f10fd11df27ca6a9b3238cdd42fa72cd3Patch
- https://git.kernel.org/stable/c/2becaa990b93cbd2928292c0b669d3abb6cf06d4Patch
- https://git.kernel.org/stable/c/33645d3e22720cac1e4548f8fef57bf0649536eePatch
- https://git.kernel.org/stable/c/348714018139c39533c55661a0c7c990671396b4Patch
- https://git.kernel.org/stable/c/548ec0805c399c65ed66c6641be467f717833ab5Patch
- https://git.kernel.org/stable/c/e0759696de6851d7536efddfdd2dfed4c4df1f09Patch
- https://git.kernel.org/stable/c/eeb0711801f5e19ef654371b627682aed3b11373Patch
- https://git.kernel.org/stable/c/04a8d07f3d58308b92630045560799a3faa3ebcePatch
- https://git.kernel.org/stable/c/148c816f10fd11df27ca6a9b3238cdd42fa72cd3Patch
- https://git.kernel.org/stable/c/2becaa990b93cbd2928292c0b669d3abb6cf06d4Patch
- https://git.kernel.org/stable/c/33645d3e22720cac1e4548f8fef57bf0649536eePatch
- https://git.kernel.org/stable/c/348714018139c39533c55661a0c7c990671396b4Patch
- https://git.kernel.org/stable/c/548ec0805c399c65ed66c6641be467f717833ab5Patch
- https://git.kernel.org/stable/c/e0759696de6851d7536efddfdd2dfed4c4df1f09Patch
- https://git.kernel.org/stable/c/eeb0711801f5e19ef654371b627682aed3b11373Patch
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.