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NFSv4: Fix up RCU annotations for struct nfs_netns_client

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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@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Trond Myklebust 2020-10-14 15:22:11 -04:00 committed by Anna Schumaker
parent 61ca2c4afd
commit 094eca3719
2 changed files with 9 additions and 4 deletions
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11
fs/nfs/sysfs.c
View File

@ -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);
}

2
fs/nfs/sysfs.h
View File

@ -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;