SUNRPC: Fix RPC client cleaned up the freed pipefs dentries

commit bfca5fb upstream.

RPC client pipefs dentries cleanup is in separated rpc_remove_pipedir()
workqueue,which takes care about pipefs superblock locking.
In some special scenarios, when kernel frees the pipefs sb of the
current client and immediately alloctes a new pipefs sb,
rpc_remove_pipedir function would misjudge the existence of pipefs
sb which is not the one it used to hold. As a result,
the rpc_remove_pipedir would clean the released freed pipefs dentries.

To fix this issue, rpc_remove_pipedir should check whether the
current pipefs sb is consistent with the original pipefs sb.

This error can be catched by KASAN:
=========================================================
[  250.497700] BUG: KASAN: slab-use-after-free in dget_parent+0x195/0x200
[  250.498315] Read of size 4 at addr ffff88800a2ab804 by task kworker/0:18/106503
[  250.500549] Workqueue: events rpc_free_client_work
[  250.501001] Call Trace:
[  250.502880]  kasan_report+0xb6/0xf0
[  250.503209]  ? dget_parent+0x195/0x200
[  250.503561]  dget_parent+0x195/0x200
[  250.503897]  ? __pfx_rpc_clntdir_depopulate+0x10/0x10
[  250.504384]  rpc_rmdir_depopulate+0x1b/0x90
[  250.504781]  rpc_remove_client_dir+0xf5/0x150
[  250.505195]  rpc_free_client_work+0xe4/0x230
[  250.505598]  process_one_work+0x8ee/0x13b0
...
[   22.039056] Allocated by task 244:
[   22.039390]  kasan_save_stack+0x22/0x50
[   22.039758]  kasan_set_track+0x25/0x30
[   22.040109]  __kasan_slab_alloc+0x59/0x70
[   22.040487]  kmem_cache_alloc_lru+0xf0/0x240
[   22.040889]  __d_alloc+0x31/0x8e0
[   22.041207]  d_alloc+0x44/0x1f0
[   22.041514]  __rpc_lookup_create_exclusive+0x11c/0x140
[   22.041987]  rpc_mkdir_populate.constprop.0+0x5f/0x110
[   22.042459]  rpc_create_client_dir+0x34/0x150
[   22.042874]  rpc_setup_pipedir_sb+0x102/0x1c0
[   22.043284]  rpc_client_register+0x136/0x4e0
[   22.043689]  rpc_new_client+0x911/0x1020
[   22.044057]  rpc_create_xprt+0xcb/0x370
[   22.044417]  rpc_create+0x36b/0x6c0
...
[   22.049524] Freed by task 0:
[   22.049803]  kasan_save_stack+0x22/0x50
[   22.050165]  kasan_set_track+0x25/0x30
[   22.050520]  kasan_save_free_info+0x2b/0x50
[   22.050921]  __kasan_slab_free+0x10e/0x1a0
[   22.051306]  kmem_cache_free+0xa5/0x390
[   22.051667]  rcu_core+0x62c/0x1930
[   22.051995]  __do_softirq+0x165/0x52a
[   22.052347]
[   22.052503] Last potentially related work creation:
[   22.052952]  kasan_save_stack+0x22/0x50
[   22.053313]  __kasan_record_aux_stack+0x8e/0xa0
[   22.053739]  __call_rcu_common.constprop.0+0x6b/0x8b0
[   22.054209]  dentry_free+0xb2/0x140
[   22.054540]  __dentry_kill+0x3be/0x540
[   22.054900]  shrink_dentry_list+0x199/0x510
[   22.055293]  shrink_dcache_parent+0x190/0x240
[   22.055703]  do_one_tree+0x11/0x40
[   22.056028]  shrink_dcache_for_umount+0x61/0x140
[   22.056461]  generic_shutdown_super+0x70/0x590
[   22.056879]  kill_anon_super+0x3a/0x60
[   22.057234]  rpc_kill_sb+0x121/0x200

Fixes: 0157d02 ("SUNRPC: handle RPC client pipefs dentries by network namespace aware routines")
Signed-off-by: felix <fuzhen5@huawei.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Hagar Hemdan <hagarhem@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/sunrpc/clnt.h

@@ -70,6 +70,7 @@ struct rpc_clnt {
  struct dentry *cl_debugfs; /* debugfs directory */
 #endif
  struct rpc_xprt_iter cl_xpi;
+ struct super_block *pipefs_sb;
 };
 
 /*

net/sunrpc/clnt.c

@@ -112,7 +112,8 @@ static void rpc_clnt_remove_pipedir(struct rpc_clnt *clnt)
 
  pipefs_sb = rpc_get_sb_net(net);
  if (pipefs_sb) {
- __rpc_clnt_remove_pipedir(clnt);
+ if (pipefs_sb == clnt->pipefs_sb)
+ __rpc_clnt_remove_pipedir(clnt);
  rpc_put_sb_net(net);
  }
 }
@@ -152,6 +153,8 @@ rpc_setup_pipedir(struct super_block *pipefs_sb, struct rpc_clnt *clnt)
 {
  struct dentry *dentry;
 
+ clnt->pipefs_sb = pipefs_sb;
+
  if (clnt->cl_program->pipe_dir_name != NULL) {
  dentry = rpc_setup_pipedir_sb(pipefs_sb, clnt);
  if (IS_ERR(dentry))