mirror of https://gitee.com/openkylin/linux.git
NLM: Fix a circular lock dependency in lockd
The problem is that the garbage collector for the 'host' structures nlm_gc_hosts(), holds nlm_host_mutex while calling down to nlmsvc_mark_resources, which, eventually takes the file->f_mutex. We cannot therefore call nlmsvc_lookup_host() from within nlmsvc_create_block, since the caller will already hold file->f_mutex, so the attempt to grab nlm_host_mutex may deadlock. Fix the problem by calling nlmsvc_lookup_host() outside the file->f_mutex. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -171,19 +171,14 @@ nlmsvc_find_block(struct nlm_cookie *cookie)
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* GRANTED_RES message by cookie, without having to rely on the client's IP
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* address. --okir
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*/
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static inline struct nlm_block *
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nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
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struct nlm_lock *lock, struct nlm_cookie *cookie)
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static struct nlm_block *
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nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
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struct nlm_file *file, struct nlm_lock *lock,
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struct nlm_cookie *cookie)
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{
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struct nlm_block *block;
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struct nlm_host *host;
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struct nlm_rqst *call = NULL;
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/* Create host handle for callback */
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host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
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if (host == NULL)
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return NULL;
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call = nlm_alloc_call(host);
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if (call == NULL)
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return NULL;
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@ -366,6 +361,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
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struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
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{
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struct nlm_block *block = NULL;
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struct nlm_host *host;
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int error;
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__be32 ret;
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@ -377,6 +373,10 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
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(long long)lock->fl.fl_end,
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wait);
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/* Create host handle for callback */
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host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
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if (host == NULL)
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return nlm_lck_denied_nolocks;
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/* Lock file against concurrent access */
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mutex_lock(&file->f_mutex);
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@ -385,7 +385,8 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
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*/
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block = nlmsvc_lookup_block(file, lock);
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if (block == NULL) {
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block = nlmsvc_create_block(rqstp, file, lock, cookie);
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block = nlmsvc_create_block(rqstp, nlm_get_host(host), file,
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lock, cookie);
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ret = nlm_lck_denied_nolocks;
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if (block == NULL)
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goto out;
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@ -449,6 +450,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
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out:
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mutex_unlock(&file->f_mutex);
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nlmsvc_release_block(block);
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nlm_release_host(host);
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dprintk("lockd: nlmsvc_lock returned %u\n", ret);
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return ret;
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}
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@ -477,10 +479,15 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
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if (block == NULL) {
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struct file_lock *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
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struct nlm_host *host;
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if (conf == NULL)
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return nlm_granted;
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block = nlmsvc_create_block(rqstp, file, lock, cookie);
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/* Create host handle for callback */
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host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
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if (host == NULL)
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return nlm_lck_denied_nolocks;
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block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
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if (block == NULL) {
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kfree(conf);
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return nlm_granted;
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