CVE-2022-50241

In the Linux kernel, the following vulnerability has been resolved:

NFSD: fix use-after-free on source server when doing inter-server copy

Use-after-free occurred when the laundromat tried to free expired cpntf_state entry on the s2s_cp_stateids list after inter-server copy completed. The sc_cp_list that the expired copy state was inserted on was already freed.

When COPY completes, the Linux client normally sends LOCKU(lock_state x), FREE_STATEID(lock_state x) and CLOSE(open_state y) to the source server. The nfs4_put_stid call from nfsd4_free_stateid cleans up the copy state from the s2s_cp_stateids list before freeing the lock states stid.

However, sometimes the CLOSE was sent before the FREE_STATEID request. When this happens, the nfsd4_close_open_stateid call from nfsd4_close frees all lock states on its st_locks list without cleaning up the copy state on the sc_cp_list list. When the time the FREE_STATEID arrives the server returns BAD_STATEID since the lock state was freed. This causes the use-after-free error to occur when the laundromat tries to free the expired cpntf_state.

This patch adds a call to nfs4_free_cpntf_statelist in nfsd4_close_open_stateid to clean up the copy state before calling free_ol_stateid_reaplist to free the lock states stid on the reaplist.

Affected Software

References

• https://git.kernel.org/stable/c/019805fea91599b22dfa62ffb29c022f35abeb06
• https://git.kernel.org/stable/c/35aa0fb8c3033a3d78603356e96fc18c5b9cceb2
• https://git.kernel.org/stable/c/6ea71246b7a02af675d733e72d14bd0d591d5f4a
• https://git.kernel.org/stable/c/83b94969751a691347606dbe6b1865efcfa5a643
• https://git.kernel.org/stable/c/bbacfcde5fff25ac22597e8373a065c647da6738