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: 0157d021d23a ("SUNRPC: handle RPC client pipefs dentries by network namespace aware routines")
Signed-off-by: felix <fuzhen5@xxxxxxxxxx>
---
include/linux/sunrpc/clnt.h | 1 +
net/sunrpc/clnt.c | 5 ++++-
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index af7358277f1c..e9d4377d03c6 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -92,6 +92,7 @@ struct rpc_clnt {
};
const struct cred *cl_cred;
unsigned int cl_max_connect; /* max number of transports not to the same IP */
+ struct super_block *pipefs_sb;
};
/*
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 9c210273d06b..f035cf0d138d 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -111,7 +111,8 @@ 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);
}
}
@@ -151,6 +152,8 @@ 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))
--
2.34.1
