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NFSv4: Fix races in the legacy idmapper upcall

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commit 51fd2eb52c0ca8275a906eed81878ef50ae94eb0 upstream.

nfs_idmap_instantiate() will cause the process that is waiting in
request_key_with_auxdata() to wake up and exit. If there is a second
process waiting for the idmap->idmap_mutex, then it may wake up and
start a new call to request_key_with_auxdata(). If the call to
idmap_pipe_downcall() from the first process has not yet finished
calling nfs_idmap_complete_pipe_upcall_locked(), then we may end up
triggering the WARN_ON_ONCE() in nfs_idmap_prepare_pipe_upcall().

The fix is to ensure that we clear idmap->idmap_upcall_data before
calling nfs_idmap_instantiate().

Fixes: e9ab41b620e4 ("NFSv4: Clean up the legacy idmapper upcall")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Trond Myklebust 2022-07-13 17:46:52 -04:00 committed by Greg Kroah-Hartman
parent d53194707d
commit 7c9699654a
1 changed files with 24 additions and 22 deletions
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46
fs/nfs/nfs4idmap.c
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@ -543,22 +543,20 @@ nfs_idmap_prepare_pipe_upcall(struct idmap *idmap,
return true;
}
static void
nfs_idmap_complete_pipe_upcall_locked(struct idmap *idmap, int ret)
static void nfs_idmap_complete_pipe_upcall(struct idmap_legacy_upcalldata *data,
int ret)
{
struct key *authkey = idmap->idmap_upcall_data->authkey;
kfree(idmap->idmap_upcall_data);
idmap->idmap_upcall_data = NULL;
complete_request_key(authkey, ret);
key_put(authkey);
complete_request_key(data->authkey, ret);
key_put(data->authkey);
kfree(data);
}
static void
nfs_idmap_abort_pipe_upcall(struct idmap *idmap, int ret)
static void nfs_idmap_abort_pipe_upcall(struct idmap *idmap,
struct idmap_legacy_upcalldata *data,
int ret)
{
if (idmap->idmap_upcall_data != NULL)
nfs_idmap_complete_pipe_upcall_locked(idmap, ret);
if (cmpxchg(&idmap->idmap_upcall_data, data, NULL) == data)
nfs_idmap_complete_pipe_upcall(data, ret);
}
static int nfs_idmap_legacy_upcall(struct key *authkey, void *aux)
@ -595,7 +593,7 @@ static int nfs_idmap_legacy_upcall(struct key *authkey, void *aux)
ret = rpc_queue_upcall(idmap->idmap_pipe, msg);
if (ret < 0)
nfs_idmap_abort_pipe_upcall(idmap, ret);
nfs_idmap_abort_pipe_upcall(idmap, data, ret);
return ret;
out2:
@ -651,6 +649,7 @@ idmap_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
struct request_key_auth *rka;
struct rpc_inode *rpci = RPC_I(file_inode(filp));
struct idmap *idmap = (struct idmap *)rpci->private;
struct idmap_legacy_upcalldata *data;
struct key *authkey;
struct idmap_msg im;
size_t namelen_in;
@ -660,10 +659,11 @@ idmap_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
* 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.
*/
if (idmap->idmap_upcall_data == NULL)
data = xchg(&idmap->idmap_upcall_data, NULL);
if (data == NULL)
goto out_noupcall;
authkey = idmap->idmap_upcall_data->authkey;
authkey = data->authkey;
rka = get_request_key_auth(authkey);
if (mlen != sizeof(im)) {
@ -685,18 +685,17 @@ idmap_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
if (namelen_in == 0 || namelen_in == IDMAP_NAMESZ) {
ret = -EINVAL;
goto out;
}
}
ret = nfs_idmap_read_and_verify_message(&im,
&idmap->idmap_upcall_data->idmap_msg,
rka->target_key, authkey);
ret = nfs_idmap_read_and_verify_message(&im, &data->idmap_msg,
rka->target_key, authkey);
if (ret >= 0) {
key_set_timeout(rka->target_key, nfs_idmap_cache_timeout);
ret = mlen;
}
out:
nfs_idmap_complete_pipe_upcall_locked(idmap, ret);
nfs_idmap_complete_pipe_upcall(data, ret);
out_noupcall:
return ret;
}
@ -710,7 +709,7 @@ idmap_pipe_destroy_msg(struct rpc_pipe_msg *msg)
struct idmap *idmap = data->idmap;
if (msg->errno)
nfs_idmap_abort_pipe_upcall(idmap, msg->errno);
nfs_idmap_abort_pipe_upcall(idmap, data, msg->errno);
}
static void
@ -718,8 +717,11 @@ idmap_release_pipe(struct inode *inode)
{
struct rpc_inode *rpci = RPC_I(inode);
struct idmap *idmap = (struct idmap *)rpci->private;
struct idmap_legacy_upcalldata *data;
nfs_idmap_abort_pipe_upcall(idmap, -EPIPE);
data = xchg(&idmap->idmap_upcall_data, NULL);
if (data)
nfs_idmap_complete_pipe_upcall(data, -EPIPE);
}
int nfs_map_name_to_uid(const struct nfs_server *server, const char *name, size_t namelen, kuid_t *uid)