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ipc/util.c: use ipc_rcu_putref() for failues in ipc_addid()

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ipc_addid() is impossible to use:
- for certain failures, the caller must not use ipc_rcu_putref(),
  because the reference counter is not yet initialized.
- for other failures, the caller must use ipc_rcu_putref(),
  because parallel operations could be ongoing already.

The patch cleans that up, by initializing the refcount early, and by
modifying all callers.

The issues is related to the finding of
[email protected]: syzbot found an
issue with reading kern_ipc_perm.seq, here both read and write to already
released memory could happen.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Manfred Spraul <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Michal Hocko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Manfred Spraul 2018-08-21 22:01:29 -07:00 • committed by Linus Torvalds
commit 39cfffd774
4 changed files with 12 additions and 4 deletions
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2
ipc/sem.c
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@ -557,7 +557,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
/* ipc_addid() locks sma upon success. */
retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
if (retval < 0) {
call_rcu(&sma->sem_perm.rcu, sem_rcu_free);
ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
return retval;
}
ns->used_sems += nsems;