diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/futex.c | 93 | ||||
| -rw-r--r-- | kernel/notifier.c | 2 | ||||
| -rw-r--r-- | kernel/sys.c | 2 |
3 files changed, 58 insertions, 39 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 0cf84c8664f2..82dfacb3250e 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -385,9 +385,9 @@ static inline int hb_waiters_pending(struct futex_hash_bucket *hb) */ static struct futex_hash_bucket *hash_futex(union futex_key *key) { - u32 hash = jhash2((u32*)&key->both.word, - (sizeof(key->both.word)+sizeof(key->both.ptr))/4, + u32 hash = jhash2((u32 *)key, offsetof(typeof(*key), both.offset) / 4, key->both.offset); + return &futex_queues[hash & (futex_hashsize - 1)]; } @@ -429,7 +429,7 @@ static void get_futex_key_refs(union futex_key *key) switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { case FUT_OFF_INODE: - ihold(key->shared.inode); /* implies smp_mb(); (B) */ + smp_mb(); /* explicit smp_mb(); (B) */ break; case FUT_OFF_MMSHARED: futex_get_mm(key); /* implies smp_mb(); (B) */ @@ -463,7 +463,6 @@ static void drop_futex_key_refs(union futex_key *key) switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { case FUT_OFF_INODE: - iput(key->shared.inode); break; case FUT_OFF_MMSHARED: mmdrop(key->private.mm); @@ -505,6 +504,46 @@ futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout, return timeout; } +/* + * Generate a machine wide unique identifier for this inode. + * + * This relies on u64 not wrapping in the life-time of the machine; which with + * 1ns resolution means almost 585 years. + * + * This further relies on the fact that a well formed program will not unmap + * the file while it has a (shared) futex waiting on it. This mapping will have + * a file reference which pins the mount and inode. + * + * If for some reason an inode gets evicted and read back in again, it will get + * a new sequence number and will _NOT_ match, even though it is the exact same + * file. + * + * It is important that match_futex() will never have a false-positive, esp. + * for PI futexes that can mess up the state. The above argues that false-negatives + * are only possible for malformed programs. + */ +static u64 get_inode_sequence_number(struct inode *inode) +{ + static atomic64_t i_seq; + u64 old; + + /* Does the inode already have a sequence number? */ + old = atomic64_read(&inode->i_sequence); + if (likely(old)) + return old; + + for (;;) { + u64 new = atomic64_add_return(1, &i_seq); + if (WARN_ON_ONCE(!new)) + continue; + + old = atomic64_cmpxchg_relaxed(&inode->i_sequence, 0, new); + if (old) + return old; + return new; + } +} + /** * get_futex_key() - Get parameters which are the keys for a futex * @uaddr: virtual address of the futex @@ -517,9 +556,15 @@ futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout, * * The key words are stored in @key on success. * - * For shared mappings, it's (page->index, file_inode(vma->vm_file), - * offset_within_page). For private mappings, it's (uaddr, current->mm). - * We can usually work out the index without swapping in the page. + * For shared mappings (when @fshared), the key is: + * ( inode->i_sequence, page->index, offset_within_page ) + * [ also see get_inode_sequence_number() ] + * + * For private mappings (or when !@fshared), the key is: + * ( current->mm, address, 0 ) + * + * This allows (cross process, where applicable) identification of the futex + * without keeping the page pinned for the duration of the FUTEX_WAIT. * * lock_page() might sleep, the caller should not hold a spinlock. */ @@ -659,8 +704,6 @@ again: key->private.mm = mm; key->private.address = address; - get_futex_key_refs(key); /* implies smp_mb(); (B) */ - } else { struct inode *inode; @@ -692,40 +735,14 @@ again: goto again; } - /* - * Take a reference unless it is about to be freed. Previously - * this reference was taken by ihold under the page lock - * pinning the inode in place so i_lock was unnecessary. The - * only way for this check to fail is if the inode was - * truncated in parallel which is almost certainly an - * application bug. In such a case, just retry. - * - * We are not calling into get_futex_key_refs() in file-backed - * cases, therefore a successful atomic_inc return below will - * guarantee that get_futex_key() will still imply smp_mb(); (B). - */ - if (!atomic_inc_not_zero(&inode->i_count)) { - rcu_read_unlock(); - put_page(page); - - goto again; - } - - /* Should be impossible but lets be paranoid for now */ - if (WARN_ON_ONCE(inode->i_mapping != mapping)) { - err = -EFAULT; - rcu_read_unlock(); - iput(inode); - - goto out; - } - key->both.offset |= FUT_OFF_INODE; /* inode-based key */ - key->shared.inode = inode; + key->shared.i_seq = get_inode_sequence_number(inode); key->shared.pgoff = basepage_index(tail); rcu_read_unlock(); } + get_futex_key_refs(key); /* implies smp_mb(); (B) */ + out: put_page(page); return err; diff --git a/kernel/notifier.c b/kernel/notifier.c index 63d7501ac638..5989bbb93039 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -519,7 +519,7 @@ NOKPROBE_SYMBOL(notify_die); int register_die_notifier(struct notifier_block *nb) { - vmalloc_sync_all(); + vmalloc_sync_mappings(); return atomic_notifier_chain_register(&die_chain, nb); } EXPORT_SYMBOL_GPL(register_die_notifier); diff --git a/kernel/sys.c b/kernel/sys.c index f9bc5c303e3f..d325f3ab624a 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -47,6 +47,7 @@ #include <linux/syscalls.h> #include <linux/kprobes.h> #include <linux/user_namespace.h> +#include <linux/time_namespace.h> #include <linux/binfmts.h> #include <linux/sched.h> @@ -2546,6 +2547,7 @@ static int do_sysinfo(struct sysinfo *info) memset(info, 0, sizeof(struct sysinfo)); ktime_get_boottime_ts64(&tp); + timens_add_boottime(&tp); info->uptime = tp.tv_sec + (tp.tv_nsec ? 1 : 0); get_avenrun(info->loads, 0, SI_LOAD_SHIFT - FSHIFT); |