Tracker / CVE-2021-47506
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.
Affected products and versions
| linux | linux_kernel |
|---|---|
| linux | linux_kernel · … → 4.4.296 |
| linux | linux_kernel · 4.10 → 4.14.259 |
| linux | linux_kernel · 4.15 → 4.19.222 |
| linux | linux_kernel · 4.20 → 5.4.168 |
| linux | linux_kernel · 4.5 → 4.9.294 |
| linux | linux_kernel · 5.11 → 5.15.8 |
| linux | linux_kernel · 5.5 → 5.10.85 |