Critical · published May 24, 2024
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.
| Product | Versions | Fixed in |
|---|---|---|
| linux/linux_kernel | < 4.4.296 | 4.4.296 |
| linux/linux_kernel | ≥ 4.5, < 4.9.294 | 4.9.294 |
| linux/linux_kernel | ≥ 4.10, < 4.14.259 | 4.14.259 |
| linux/linux_kernel | ≥ 4.15, < 4.19.222 | 4.19.222 |
| linux/linux_kernel | ≥ 4.20, < 5.4.168 | 5.4.168 |
| linux/linux_kernel | ≥ 5.5, < 5.10.85 | 5.10.85 |
| linux/linux_kernel | ≥ 5.11, < 5.15.8 | 5.15.8 |
| linux/linux_kernel | all versions | — |
| linux/linux_kernel | all versions | — |
| linux/linux_kernel | all versions | — |
| linux/linux_kernel | all versions | — |