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:
[<ffffffff81260878>] ? __key_instantiate_and_link+0x58/0x100
[<ffffffff81260983>] key_instantiate_and_link+0x63/0xa0
[<ffffffffa057062b>] idmap_pipe_downcall+0x1cb/0x1e0 [nfs]
[<ffffffffa0107f57>] rpc_pipe_write+0x67/0x90 [sunrpc]
[<ffffffff8117f833>] vfs_write+0xb3/0x180
[<ffffffff8117fb5a>] sys_write+0x4a/0x90
[<ffffffff81600329>] system_call_fastpath+0x16/0x1b
Code: Bad RIP value.
RIP [< (null)>] (null)
RSP <ffff8801a3645d40>
CR2: 0000000000000000
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Reviewed-by: Steve Dickson <steved@xxxxxxxxxx>
---
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 864c51e..1b5058b 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 @@ out2:
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;
}
--
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