diff options
Diffstat (limited to 'kernel/ucount.c')
| -rw-r--r-- | kernel/ucount.c | 65 |
1 files changed, 60 insertions, 5 deletions
diff --git a/kernel/ucount.c b/kernel/ucount.c index bb51849e6375..4f5613dac227 100644 --- a/kernel/ucount.c +++ b/kernel/ucount.c @@ -150,9 +150,15 @@ static void hlist_add_ucounts(struct ucounts *ucounts) spin_unlock_irq(&ucounts_lock); } +static inline bool get_ucounts_or_wrap(struct ucounts *ucounts) +{ + /* Returns true on a successful get, false if the count wraps. */ + return !atomic_add_negative(1, &ucounts->count); +} + struct ucounts *get_ucounts(struct ucounts *ucounts) { - if (ucounts && atomic_add_negative(1, &ucounts->count)) { + if (!get_ucounts_or_wrap(ucounts)) { put_ucounts(ucounts); ucounts = NULL; } @@ -163,7 +169,7 @@ struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) { struct hlist_head *hashent = ucounts_hashentry(ns, uid); struct ucounts *ucounts, *new; - long overflow; + bool wrapped; spin_lock_irq(&ucounts_lock); ucounts = find_ucounts(ns, uid, hashent); @@ -188,9 +194,9 @@ struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) return new; } } - overflow = atomic_add_negative(1, &ucounts->count); + wrapped = !get_ucounts_or_wrap(ucounts); spin_unlock_irq(&ucounts_lock); - if (overflow) { + if (wrapped) { put_ucounts(ucounts); return NULL; } @@ -276,7 +282,7 @@ bool dec_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) struct ucounts *iter; long new = -1; /* Silence compiler warning */ for (iter = ucounts; iter; iter = iter->ns->ucounts) { - long dec = atomic_long_add_return(-v, &iter->ucount[type]); + long dec = atomic_long_sub_return(v, &iter->ucount[type]); WARN_ON_ONCE(dec < 0); if (iter == ucounts) new = dec; @@ -284,6 +290,55 @@ bool dec_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) return (new == 0); } +static void do_dec_rlimit_put_ucounts(struct ucounts *ucounts, + struct ucounts *last, enum ucount_type type) +{ + struct ucounts *iter, *next; + for (iter = ucounts; iter != last; iter = next) { + long dec = atomic_long_sub_return(1, &iter->ucount[type]); + WARN_ON_ONCE(dec < 0); + next = iter->ns->ucounts; + if (dec == 0) + put_ucounts(iter); + } +} + +void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum ucount_type type) +{ + do_dec_rlimit_put_ucounts(ucounts, NULL, type); +} + +long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum ucount_type type) +{ + /* Caller must hold a reference to ucounts */ + struct ucounts *iter; + long dec, ret = 0; + + for (iter = ucounts; iter; iter = iter->ns->ucounts) { + long max = READ_ONCE(iter->ns->ucount_max[type]); + long new = atomic_long_add_return(1, &iter->ucount[type]); + if (new < 0 || new > max) + goto unwind; + if (iter == ucounts) + ret = new; + /* + * Grab an extra ucount reference for the caller when + * the rlimit count was previously 0. + */ + if (new != 1) + continue; + if (!get_ucounts(iter)) + goto dec_unwind; + } + return ret; +dec_unwind: + dec = atomic_long_sub_return(1, &iter->ucount[type]); + WARN_ON_ONCE(dec < 0); +unwind: + do_dec_rlimit_put_ucounts(ucounts, iter, type); + return 0; +} + bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsigned long max) { struct ucounts *iter; |