From a427b9ec4eda8cd6e641ea24541d30b641fc3140 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 25 Jul 2012 16:53:36 +0100 Subject: [PATCH] NFS: Fix a number of bugs in the idmapper Fix a number of bugs in the NFS idmapper code: (1) Only registered key types can be passed to the core keys code, so register the legacy idmapper key type. This is a requirement because the unregister function cleans up keys belonging to that key type so that there aren't dangling pointers to the module left behind - including the key->type pointer. (2) Rename the legacy key type. You can't have two key types with the same name, and (1) would otherwise require that. (3) complete_request_key() must be called in the error path of nfs_idmap_legacy_upcall(). (4) There is one idmap struct for each nfs_client struct. This means that idmap->idmap_key_cons is shared without the use of a lock. This is a problem because key_instantiate_and_link() - as called indirectly by idmap_pipe_downcall() - releases anyone waiting for the key to be instantiated. What happens is that idmap_pipe_downcall() running in the rpc.idmapd thread, releases the NFS filesystem in whatever thread that is running in to continue. This may then make another idmapper call, overwriting idmap_key_cons before idmap_pipe_downcall() gets the chance to call complete_request_key(). I *think* that reading idmap_key_cons only once, before key_instantiate_and_link() is called, and then caching the result in a variable is sufficient. Bug (4) is the cause of: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [< (null)>] (null) PGD 0 Oops: 0010 [#1] SMP CPU 1 Modules linked in: ppdev parport_pc lp parport ip6table_filter ip6_tables ebtable_nat ebtables ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack nfs fscache xt_CHECKSUM auth_rpcgss iptable_mangle nfs_acl bridge stp llc lockd be2iscsi iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4 cxgb3i libcxgbi cxgb3 mdio ib_iser rdma_cm ib_cm iw_cm ib_sa ib_mad ib_core ib_addr iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi snd_hda_codec_realtek snd_usb_audio snd_hda_intel snd_hda_codec snd_seq snd_pcm snd_hwdep snd_usbmidi_lib snd_rawmidi snd_timer uvcvideo videobuf2_core videodev media videobuf2_vmalloc snd_seq_device videobuf2_memops e1000e vhost_net iTCO_wdt joydev coretemp snd soundcore macvtap macvlan i2c_i801 snd_page_alloc tun iTCO_vendor_support microcode kvm_intel kvm sunrpc hid_logitech_dj usb_storage i915 drm_kms_helper drm i2c_algo_bit i2c_core video [last unloaded: scsi_wait_scan] Pid: 1229, comm: rpc.idmapd Not tainted 3.4.2-1.fc16.x86_64 #1 Gateway DX4710-UB801A/G33M05G1 RIP: 0010:[<0000000000000000>] [< (null)>] (null) RSP: 0018:ffff8801a3645d40 EFLAGS: 00010246 RAX: ffff880077707e30 RBX: ffff880077707f50 RCX: ffff8801a18ccd80 RDX: 0000000000000006 RSI: ffff8801a3645e75 RDI: ffff880077707f50 RBP: ffff8801a3645d88 R08: ffff8801a430f9c0 R09: ffff8801a3645db0 R10: 000000000000000a R11: 0000000000000246 R12: ffff8801a18ccd80 R13: ffff8801a3645e75 R14: ffff8801a430f9c0 R15: 0000000000000006 FS: 00007fb6fb51a700(0000) GS:ffff8801afc80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 00000001a49b0000 CR4: 00000000000027e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process rpc.idmapd (pid: 1229, threadinfo ffff8801a3644000, task ffff8801a3bf9710) Stack: ffffffff81260878 ffff8801a3645db0 ffff8801a3645db0 ffff880077707a90 ffff880077707f50 ffff8801a18ccd80 0000000000000006 ffff8801a3645e75 ffff8801a430f9c0 ffff8801a3645dd8 ffffffff81260983 ffff8801a3645de8 Call Trace: [] ? __key_instantiate_and_link+0x58/0x100 [] key_instantiate_and_link+0x63/0xa0 [] idmap_pipe_downcall+0x1cb/0x1e0 [nfs] [] rpc_pipe_write+0x67/0x90 [sunrpc] [] vfs_write+0xb3/0x180 [] sys_write+0x4a/0x90 [] system_call_fastpath+0x16/0x1b Code: Bad RIP value. RIP [< (null)>] (null) RSP CR2: 0000000000000000 Signed-off-by: David Howells Reviewed-by: Steve Dickson Signed-off-by: Trond Myklebust Cc: stable@vger.kernel.org [>= 3.4] --- fs/nfs/idmap.c | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c index 864c51e4b400..1b5058b4043b 100644 --- a/fs/nfs/idmap.c +++ b/fs/nfs/idmap.c @@ -205,12 +205,18 @@ static int nfs_idmap_init_keyring(void) if (ret < 0) goto failed_put_key; + ret = register_key_type(&key_type_id_resolver_legacy); + if (ret < 0) + goto failed_reg_legacy; + set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags); cred->thread_keyring = keyring; cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; id_resolver_cache = cred; return 0; +failed_reg_legacy: + unregister_key_type(&key_type_id_resolver); failed_put_key: key_put(keyring); failed_put_cred: @@ -222,6 +228,7 @@ static void nfs_idmap_quit_keyring(void) { key_revoke(id_resolver_cache->thread_keyring); unregister_key_type(&key_type_id_resolver); + unregister_key_type(&key_type_id_resolver_legacy); put_cred(id_resolver_cache); } @@ -385,7 +392,7 @@ static const struct rpc_pipe_ops idmap_upcall_ops = { }; static struct key_type key_type_id_resolver_legacy = { - .name = "id_resolver", + .name = "id_legacy", .instantiate = user_instantiate, .match = user_match, .revoke = user_revoke, @@ -674,6 +681,7 @@ static int nfs_idmap_legacy_upcall(struct key_construction *cons, if (ret < 0) goto out2; + BUG_ON(idmap->idmap_key_cons != NULL); idmap->idmap_key_cons = cons; ret = rpc_queue_upcall(idmap->idmap_pipe, msg); @@ -687,8 +695,7 @@ static int nfs_idmap_legacy_upcall(struct key_construction *cons, out1: kfree(msg); out0: - key_revoke(cons->key); - key_revoke(cons->authkey); + complete_request_key(cons, ret); return ret; } @@ -722,11 +729,18 @@ idmap_pipe_downcall(struct file *filp, const char __user *src, size_t mlen) { struct rpc_inode *rpci = RPC_I(filp->f_path.dentry->d_inode); struct idmap *idmap = (struct idmap *)rpci->private; - struct key_construction *cons = idmap->idmap_key_cons; + struct key_construction *cons; struct idmap_msg im; size_t namelen_in; int ret; + /* If instantiation is successful, anyone waiting for key construction + * will have been woken up and someone else may now have used + * idmap_key_cons - so after this point we may no longer touch it. + */ + cons = ACCESS_ONCE(idmap->idmap_key_cons); + idmap->idmap_key_cons = NULL; + if (mlen != sizeof(im)) { ret = -ENOSPC; goto out; @@ -739,7 +753,7 @@ idmap_pipe_downcall(struct file *filp, const char __user *src, size_t mlen) if (!(im.im_status & IDMAP_STATUS_SUCCESS)) { ret = mlen; - complete_request_key(idmap->idmap_key_cons, -ENOKEY); + complete_request_key(cons, -ENOKEY); goto out_incomplete; } @@ -756,7 +770,7 @@ idmap_pipe_downcall(struct file *filp, const char __user *src, size_t mlen) } out: - complete_request_key(idmap->idmap_key_cons, ret); + complete_request_key(cons, ret); out_incomplete: return ret; } -- GitLab