Overview
About vulnerability
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.
Details
- Affected product:
- CentOS 6 ELS , CloudLinux 6 ELS , Oracle Linux 6 ELS , Ubuntu 16.04 ELS
- Affected packages:
- kernel @ 2.6.32 (+4 more)
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.