From b10252c7ae9c9d7c90552f88b544a44ee773af64 Mon Sep 17 00:00:00 2001 From: Alexander Sverdlin Date: Tue, 7 Dec 2021 15:00:39 +0100 Subject: nfsd: Fix nsfd startup race (again) Commit bd5ae9288d64 ("nfsd: register pernet ops last, unregister first") has re-opened rpc_pipefs_event() race against nfsd_net_id registration (register_pernet_subsys()) which has been fixed by commit bb7ffbf29e76 ("nfsd: fix nsfd startup race triggering BUG_ON"). Restore the order of register_pernet_subsys() vs register_cld_notifier(). Add WARN_ON() to prevent a future regression. Crash info: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000012 CPU: 8 PID: 345 Comm: mount Not tainted 5.4.144-... #1 pc : rpc_pipefs_event+0x54/0x120 [nfsd] lr : rpc_pipefs_event+0x48/0x120 [nfsd] Call trace: rpc_pipefs_event+0x54/0x120 [nfsd] blocking_notifier_call_chain rpc_fill_super get_tree_keyed rpc_fs_get_tree vfs_get_tree do_mount ksys_mount __arm64_sys_mount el0_svc_handler el0_svc Fixes: bd5ae9288d64 ("nfsd: register pernet ops last, unregister first") Cc: stable@vger.kernel.org Signed-off-by: Alexander Sverdlin Signed-off-by: J. Bruce Fields --- fs/nfsd/nfs4recover.c | 1 + fs/nfsd/nfsctl.c | 14 +++++++------- 2 files changed, 8 insertions(+), 7 deletions(-) diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c index 6fedc49726bf..c634483d85d2 100644 --- a/fs/nfsd/nfs4recover.c +++ b/fs/nfsd/nfs4recover.c @@ -2156,6 +2156,7 @@ static struct notifier_block nfsd4_cld_block = { int register_cld_notifier(void) { + WARN_ON(!nfsd_net_id); return rpc_pipefs_notifier_register(&nfsd4_cld_block); } diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c index af8531c3854a..51a49e0cfe37 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -1521,12 +1521,9 @@ static int __init init_nfsd(void) int retval; printk(KERN_INFO "Installing knfsd (copyright (C) 1996 okir@monad.swb.de).\n"); - retval = register_cld_notifier(); - if (retval) - return retval; retval = nfsd4_init_slabs(); if (retval) - goto out_unregister_notifier; + return retval; retval = nfsd4_init_pnfs(); if (retval) goto out_free_slabs; @@ -1545,9 +1542,14 @@ static int __init init_nfsd(void) goto out_free_exports; retval = register_pernet_subsys(&nfsd_net_ops); if (retval < 0) + goto out_free_filesystem; + retval = register_cld_notifier(); + if (retval) goto out_free_all; return 0; out_free_all: + unregister_pernet_subsys(&nfsd_net_ops); +out_free_filesystem: unregister_filesystem(&nfsd_fs_type); out_free_exports: remove_proc_entry("fs/nfs/exports", NULL); @@ -1561,13 +1563,12 @@ out_free_pnfs: nfsd4_exit_pnfs(); out_free_slabs: nfsd4_free_slabs(); -out_unregister_notifier: - unregister_cld_notifier(); return retval; } static void __exit exit_nfsd(void) { + unregister_cld_notifier(); unregister_pernet_subsys(&nfsd_net_ops); nfsd_drc_slab_free(); remove_proc_entry("fs/nfs/exports", NULL); @@ -1577,7 +1578,6 @@ static void __exit exit_nfsd(void) nfsd4_free_slabs(); nfsd4_exit_pnfs(); unregister_filesystem(&nfsd_fs_type); - unregister_cld_notifier(); } MODULE_AUTHOR("Olaf Kirch "); -- cgit v1.2.3-59-g8ed1b From 548ec0805c399c65ed66c6641be467f717833ab5 Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Mon, 29 Nov 2021 15:08:00 -0500 Subject: 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. Cc: stable@vger.kernel.org Signed-off-by: J. Bruce Fields --- fs/nfsd/nfs4state.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index bfad94c70b84..1956d377d1a6 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1207,6 +1207,11 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp) return 0; } +static bool delegation_hashed(struct nfs4_delegation *dp) +{ + return !(list_empty(&dp->dl_perfile)); +} + static bool unhash_delegation_locked(struct nfs4_delegation *dp) { @@ -1214,7 +1219,7 @@ unhash_delegation_locked(struct nfs4_delegation *dp) lockdep_assert_held(&state_lock); - if (list_empty(&dp->dl_perfile)) + if (!delegation_hashed(dp)) return false; dp->dl_stid.sc_type = NFS4_CLOSED_DELEG_STID; @@ -4598,7 +4603,7 @@ static void nfsd4_cb_recall_prepare(struct nfsd4_callback *cb) * queued for a lease break. Don't queue it again. */ spin_lock(&state_lock); - if (dp->dl_time == 0) { + if (delegation_hashed(dp) && dp->dl_time == 0) { dp->dl_time = ktime_get_boottime_seconds(); list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru); } -- cgit v1.2.3-59-g8ed1b