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Merge branch 'ucount-fixes-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 

Pull ucount cleanups from Eric Biederman:
 "While working on the ucount fixes a for v5.15 a number of cleanups
  suggested themselves.

  Little things like not testing for NULL when a pointer can not be NULL
  and wrapping atomic_add_negative with a more descriptive name, so that
  people reading the code can more quickly understand what is going on"

* 'ucount-fixes-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  ucounts: Use atomic_long_sub_return for clarity
  ucounts: Add get_ucounts_or_wrap for clarity
  ucounts: Remove unnecessary test for NULL ucount in get_ucounts
  ucounts: In set_cred_ucounts assume new->ucounts is non-NULL
This commit is contained in:
Linus Torvalds 2021-11-02 15:48:37 -07:00
parent a85373fe44 32342701b4
commit 33fb42636a
2 changed files with 15 additions and 10 deletions
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5
kernel/cred.c
View File

@ -676,15 +676,14 @@ int set_cred_ucounts(struct cred *new)
* This optimization is needed because alloc_ucounts() uses locks
* for table lookups.
*/
if (old_ucounts && old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid))
if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid))
return 0;
if (!(new_ucounts = alloc_ucounts(new->user_ns, new->euid)))
return -EAGAIN;
new->ucounts = new_ucounts;
if (old_ucounts)
put_ucounts(old_ucounts);
put_ucounts(old_ucounts);
return 0;
}

20
kernel/ucount.c
View File

@ -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;
@ -289,7 +295,7 @@ static void do_dec_rlimit_put_ucounts(struct ucounts *ucounts,
{
struct ucounts *iter, *next;
for (iter = ucounts; iter != last; iter = next) {
long dec = atomic_long_add_return(-1, &iter->ucount[type]);
long dec = atomic_long_sub_return(1, &iter->ucount[type]);
WARN_ON_ONCE(dec < 0);
next = iter->ns->ucounts;
if (dec == 0)
@ -326,7 +332,7 @@ long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum ucount_type type)
}
return ret;
dec_unwind:
dec = atomic_long_add_return(-1, &iter->ucount[type]);
dec = atomic_long_sub_return(1, &iter->ucount[type]);
WARN_ON_ONCE(dec < 0);
unwind:
do_dec_rlimit_put_ucounts(ucounts, iter, type);