From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
The identifier is read as an RCU protected string. Its value may
be changed during the lifetime of the network namespace by writing
a new string into the sysfs pseudofile (at which point, we free the
old string only after a call to synchronize_rcu()).
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
fs/nfs/sysfs.c | 11 ++++++++---
fs/nfs/sysfs.h | 2 +-
2 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/fs/nfs/sysfs.c b/fs/nfs/sysfs.c
index c489496b5659..8cb70755e3c9 100644
--- a/fs/nfs/sysfs.c
+++ b/fs/nfs/sysfs.c
@@ -79,7 +79,12 @@ static ssize_t nfs_netns_identifier_show(struct kobject *kobj,
struct nfs_netns_client *c = container_of(kobj,
struct nfs_netns_client,
kobject);
- return scnprintf(buf, PAGE_SIZE, "%s\n", c->identifier);
+ ssize_t ret;
+
+ rcu_read_lock();
+ ret = scnprintf(buf, PAGE_SIZE, "%s\n", rcu_dereference(c->identifier));
+ rcu_read_unlock();
+ return ret;
}
/* Strip trailing '\n' */
@@ -107,7 +112,7 @@ static ssize_t nfs_netns_identifier_store(struct kobject *kobj,
p = kmemdup_nul(buf, len, GFP_KERNEL);
if (!p)
return -ENOMEM;
- old = xchg(&c->identifier, p);
+ old = rcu_dereference_protected(xchg(&c->identifier, (char __rcu *)p), 1);
if (old) {
synchronize_rcu();
kfree(old);
@@ -121,7 +126,7 @@ static void nfs_netns_client_release(struct kobject *kobj)
struct nfs_netns_client,
kobject);
- kfree(c->identifier);
+ kfree(rcu_dereference_raw(c->identifier));
kfree(c);
}
diff --git a/fs/nfs/sysfs.h b/fs/nfs/sysfs.h
index ebcbdc40483b..5501ef573c32 100644
--- a/fs/nfs/sysfs.h
+++ b/fs/nfs/sysfs.h
@@ -11,7 +11,7 @@
struct nfs_netns_client {
struct kobject kobject;
struct net *net;
- const char *identifier;
+ const char __rcu *identifier;
};
extern struct kobject *nfs_client_kobj;
--
2.26.2
