On Fri, 2025-01-17 at 11:32 -0500, Olga Kornievskaia wrote:
> Currently, when no active threads are running, a root user using nfsdctl
> command can try to remove a particular listener from the list of previously
> added ones, then start the server by increasing the number of threads,
> it leads to the following problem:
>
> [ 158.835354] refcount_t: addition on 0; use-after-free.
> [ 158.835603] WARNING: CPU: 2 PID: 9145 at lib/refcount.c:25 refcount_warn_saturate+0x160/0x1a0
> [ 158.836017] Modules linked in: rpcrdma rdma_cm iw_cm ib_cm ib_core nfsd auth_rpcgss nfs_acl lockd grace overlay isofs uinput snd_seq_dummy snd_hrtimer nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 rfkill ip_set nf_tables qrtr sunrpc vfat fat uvcvideo videobuf2_vmalloc videobuf2_memops uvc videobuf2_v4l2 videodev videobuf2_common snd_hda_codec_generic mc e1000e snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_hda_core snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd soundcore sg loop dm_multipath dm_mod nfnetlink vsock_loopback vmw_vsock_virtio_transport_common vmw_vsock_vmci_transport vmw_vmci vsock xfs libcrc32c crct10dif_ce ghash_ce vmwgfx sha2_ce sha256_arm64 sr_mod sha1_ce cdrom nvme drm_client_lib drm_ttm_helper ttm nvme_core drm_kms_helper nvme_auth drm fuse
> [ 158.840093] CPU: 2 UID: 0 PID: 9145 Comm: nfsd Kdump: loaded Tainted: G B W 6.13.0-rc6+ #7
> [ 158.840624] Tainted: [B]=BAD_PAGE, [W]=WARN
> [ 158.840802] Hardware name: VMware, Inc. VMware20,1/VBSA, BIOS VMW201.00V.24006586.BA64.2406042154 06/04/2024
> [ 158.841220] pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
> [ 158.841563] pc : refcount_warn_saturate+0x160/0x1a0
> [ 158.841780] lr : refcount_warn_saturate+0x160/0x1a0
> [ 158.842000] sp : ffff800089be7d80
> [ 158.842147] x29: ffff800089be7d80 x28: ffff00008e68c148 x27: ffff00008e68c148
> [ 158.842492] x26: ffff0002e3b5c000 x25: ffff600011cd1829 x24: ffff00008653c010
> [ 158.842832] x23: ffff00008653c000 x22: 1fffe00011cd1829 x21: ffff00008653c028
> [ 158.843175] x20: 0000000000000002 x19: ffff00008653c010 x18: 0000000000000000
> [ 158.843505] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> [ 158.843836] x14: 0000000000000000 x13: 0000000000000001 x12: ffff600050a26493
> [ 158.844143] x11: 1fffe00050a26492 x10: ffff600050a26492 x9 : dfff800000000000
> [ 158.844475] x8 : 00009fffaf5d9b6e x7 : ffff000285132493 x6 : 0000000000000001
> [ 158.844823] x5 : ffff000285132490 x4 : ffff600050a26493 x3 : ffff8000805e72bc
> [ 158.845174] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff000098588000
> [ 158.845528] Call trace:
> [ 158.845658] refcount_warn_saturate+0x160/0x1a0 (P)
> [ 158.845894] svc_recv+0x58c/0x680 [sunrpc]
> [ 158.846183] nfsd+0x1fc/0x348 [nfsd]
> [ 158.846390] kthread+0x274/0x2f8
> [ 158.846546] ret_from_fork+0x10/0x20
> [ 158.846714] ---[ end trace 0000000000000000 ]---
>
> nfsd_nl_listener_set_doit() would manipulate the list of transports of
> server's sv_permsocks and close the specified listener but the other
> list of transports (server's sp_xprts list) would not be changed leading
> to the problem above.
>
> Instead, determined if the nfsdctl is trying to remove a listener, in
> which case, delete all the existing listener transports and re-create
> all-but-the-removed ones.
>
> Fixes: 16a471177496 ("NFSD: add listener-{set,get} netlink command")
> Signed-off-by: Olga Kornievskaia <okorniev@xxxxxxxxxx>
> ---
> fs/nfsd/nfsctl.c | 41 ++++++++++++++++++-----------------------
> 1 file changed, 18 insertions(+), 23 deletions(-)
>
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index 95ea4393305b..079c1fe2eee7 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -1918,6 +1918,7 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
> LIST_HEAD(permsocks);
> struct nfsd_net *nn;
> int err, rem;
> + bool delete = false;
>
> mutex_lock(&nfsd_mutex);
>
> @@ -1977,35 +1978,26 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
> }
> }
>
> - /* For now, no removing old sockets while server is running */
> - if (serv->sv_nrthreads && !list_empty(&permsocks)) {
> + /* If we have listener transports left on permsocks list, it means
> + * we are asked to remove a listener
> + */
> + if (!list_empty(&permsocks)) {
> list_splice_init(&permsocks, &serv->sv_permsocks);
> - spin_unlock_bh(&serv->sv_lock);
> - err = -EBUSY;
> - goto out_unlock_mtx;
> + delete = true;
> }
> + spin_unlock_bh(&serv->sv_lock);
>
> - /* Close the remaining sockets on the permsocks list */
> - while (!list_empty(&permsocks)) {
> - xprt = list_first_entry(&permsocks, struct svc_xprt, xpt_list);
> - list_move(&xprt->xpt_list, &serv->sv_permsocks);
> -
> - /*
> - * Newly-created sockets are born with the BUSY bit set. Clear
> - * it if there are no threads, since nothing can pick it up
> - * in that case.
> + /* Not removing old listener transports while server is running */
> + if (serv->sv_nrthreads) {
> + err = -EBUSY;
> + goto out_unlock_mtx;
> + } else if (delete) {
> + /* since we can't delete a single entry, we will destroy
> + * all remaining listeners and recreate the list
> */
> - if (!serv->sv_nrthreads)
> - clear_bit(XPT_BUSY, &xprt->xpt_flags);
> -
> - set_bit(XPT_CLOSE, &xprt->xpt_flags);
> - spin_unlock_bh(&serv->sv_lock);
> - svc_xprt_close(xprt);
> - spin_lock_bh(&serv->sv_lock);
> + svc_xprt_destroy_all(serv, net);
> }
>
> - spin_unlock_bh(&serv->sv_lock);
> -
> /* walk list of addrs again, open any that still don't exist */
> nlmsg_for_each_attr(attr, info->nlhdr, GENL_HDRLEN, rem) {
> struct nlattr *tb[NFSD_A_SOCK_MAX + 1];
> @@ -2031,6 +2023,9 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
>
> xprt = svc_find_listener(serv, xcl_name, net, sa);
> if (xprt) {
> + if (delete)
> + WARN_ONCE("Transport type=%s already exists\n",
> + xcl_name);
> svc_xprt_put(xprt);
> continue;
> }
This does seem a bit safer than trying to dequeue a since entry from
the lwq.
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
