diff options
| -rw-r--r-- | kernel/module/main.c | 73 |
1 files changed, 71 insertions, 2 deletions
diff --git a/kernel/module/main.c b/kernel/module/main.c index 23abfe3e2674..d6de66a6a1ac 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -3057,15 +3057,82 @@ SYSCALL_DEFINE3(init_module, void __user *, umod, return load_module(&info, uargs, 0); } +struct idempotent { + const void *cookie; + struct hlist_node entry; + struct completion complete; + int ret; +}; + +#define IDEM_HASH_BITS 8 +static struct hlist_head idem_hash[1 << IDEM_HASH_BITS]; +static DEFINE_SPINLOCK(idem_lock); + +static bool idempotent(struct idempotent *u, const void *cookie) +{ + int hash = hash_ptr(cookie, IDEM_HASH_BITS); + struct hlist_head *head = idem_hash + hash; + struct idempotent *existing; + bool first; + + u->ret = 0; + u->cookie = cookie; + init_completion(&u->complete); + + spin_lock(&idem_lock); + first = true; + hlist_for_each_entry(existing, head, entry) { + if (existing->cookie != cookie) + continue; + first = false; + break; + } + hlist_add_head(&u->entry, idem_hash + hash); + spin_unlock(&idem_lock); + + return !first; +} + +/* + * We were the first one with 'cookie' on the list, and we ended + * up completing the operation. We now need to walk the list, + * remove everybody - which includes ourselves - fill in the return + * value, and then complete the operation. + */ +static void idempotent_complete(struct idempotent *u, int ret) +{ + const void *cookie = u->cookie; + int hash = hash_ptr(cookie, IDEM_HASH_BITS); + struct hlist_head *head = idem_hash + hash; + struct hlist_node *next; + struct idempotent *pos; + + spin_lock(&idem_lock); + hlist_for_each_entry_safe(pos, next, head, entry) { + if (pos->cookie != cookie) + continue; + hlist_del(&pos->entry); + pos->ret = ret; + complete(&pos->complete); + } + spin_unlock(&idem_lock); +} + static int init_module_from_file(struct file *f, const char __user * uargs, int flags) { + struct idempotent idem; struct load_info info = { }; void *buf = NULL; - int len; + int len, ret; if (!f || !(f->f_mode & FMODE_READ)) return -EBADF; + if (idempotent(&idem, file_inode(f))) { + wait_for_completion(&idem.complete); + return idem.ret; + } + len = kernel_read_file(f, 0, &buf, INT_MAX, NULL, READING_MODULE); if (len < 0) { mod_stat_inc(&failed_kreads); @@ -3086,7 +3153,9 @@ static int init_module_from_file(struct file *f, const char __user * uargs, int info.len = len; } - return load_module(&info, uargs, flags); + ret = load_module(&info, uargs, flags); + idempotent_complete(&idem, ret); + return ret; } SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags) |