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p_candebug(), p_cansee(): always allow for curproc

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Privilege checks in both functions should allow the current process to
infer information about itself, as well as use the interfaces that are
proclaimed 'debugging', for instance, procctl(2).

Note that in p_cansee() case, explicit comparision of curproc and p
avoids a race where the process might change credentials and cause
thread to compare its cached stale credentials against updated process
creds, effectively disallowing the process to observe itself.

Reviewed by:	emaste
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D33986
This commit is contained in:
Konstantin Belousov 2022-01-21 17:29:17 +02:00
parent 3de96d664a
commit 55a0aa2162
1 changed files with 5 additions and 3 deletions
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8
sys/kern/kern_prot.c
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@ -1460,10 +1460,12 @@ cr_cansee(struct ucred *u1, struct ucred *u2)
int
p_cansee(struct thread *td, struct proc *p)
{
/* Wrap cr_cansee() for all functionality. */
KASSERT(td == curthread, ("%s: td not curthread", __func__));
PROC_LOCK_ASSERT(p, MA_OWNED);
if (td->td_proc == p)
return (0);
return (cr_cansee(td->td_ucred, p->p_ucred));
}
@ -1681,10 +1683,10 @@ p_candebug(struct thread *td, struct proc *p)
KASSERT(td == curthread, ("%s: td not curthread", __func__));
PROC_LOCK_ASSERT(p, MA_OWNED);
if ((error = priv_check(td, PRIV_DEBUG_UNPRIV)))
return (error);
if (td->td_proc == p)
return (0);
if ((error = priv_check(td, PRIV_DEBUG_UNPRIV)))
return (error);
if ((error = prison_check(td->td_ucred, p->p_ucred)))
return (error);
#ifdef MAC