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lockd: nlm_blocked list race fixes 

This patch fixes races when lockd accesses the global nlm_blocked list.
It was mostly safe to access the list because everything was accessed
from the lockd kernel thread context but there exist cases like
nlmsvc_grant_deferred() that could manipulate the nlm_blocked list and
it can be called from any context.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Alexander Aring 2023-07-20 08:58:04 -04:00 committed by Chuck Lever
parent f2b7019d2e
commit be2be5f7f4
1 changed files with 12 additions and 1 deletions
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13
fs/lockd/svclock.c
View File

@ -131,12 +131,14 @@ static void nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
static inline void
nlmsvc_remove_block(struct nlm_block *block)
{
spin_lock(&nlm_blocked_lock);
if (!list_empty(&block->b_list)) {
spin_lock(&nlm_blocked_lock);
list_del_init(&block->b_list);
spin_unlock(&nlm_blocked_lock);
nlmsvc_release_block(block);
return;
}
spin_unlock(&nlm_blocked_lock);
}
/*
@ -152,6 +154,7 @@ nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
file, lock->fl.fl_pid,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end, lock->fl.fl_type);
spin_lock(&nlm_blocked_lock);
list_for_each_entry(block, &nlm_blocked, b_list) {
fl = &block->b_call->a_args.lock.fl;
dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
@ -161,9 +164,11 @@ nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
nlmdbg_cookie2a(&block->b_call->a_args.cookie));
if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
kref_get(&block->b_count);
spin_unlock(&nlm_blocked_lock);
return block;
}
}
spin_unlock(&nlm_blocked_lock);
return NULL;
}
@ -185,16 +190,19 @@ nlmsvc_find_block(struct nlm_cookie *cookie)
{
struct nlm_block *block;
spin_lock(&nlm_blocked_lock);
list_for_each_entry(block, &nlm_blocked, b_list) {
if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
goto found;
}
spin_unlock(&nlm_blocked_lock);
return NULL;
found:
dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
kref_get(&block->b_count);
spin_unlock(&nlm_blocked_lock);
return block;
}
@ -317,6 +325,7 @@ void nlmsvc_traverse_blocks(struct nlm_host *host,
restart:
mutex_lock(&file->f_mutex);
spin_lock(&nlm_blocked_lock);
list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
if (!match(block->b_host, host))
continue;
@ -325,11 +334,13 @@ restart:
if (list_empty(&block->b_list))
continue;
kref_get(&block->b_count);
spin_unlock(&nlm_blocked_lock);
mutex_unlock(&file->f_mutex);
nlmsvc_unlink_block(block);
nlmsvc_release_block(block);
goto restart;
}
spin_unlock(&nlm_blocked_lock);
mutex_unlock(&file->f_mutex);
}