Squish the "could sleep with process lock" messages caused by calling

uifind() with a proc lock held.

change_ruid() and change_euid() have been modified to take a uidinfo
structure which will be pre-allocated by callers, they will then
call uihold() on the uidinfo structure so that the caller's logic
is simplified.

This allows one to call uifind() before locking the proc struct and
thereby avoid a potential blocking allocation with the proc lock
held.

This may need revisiting, perhaps keeping a spare uidinfo allocated
per process to handle this situation or re-examining if the proc
lock needs to be held over the entire operation of changing real
or effective user id.

Submitted by: Don Lewis <dl-freebsd@catspoiler.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/sys/alpha/osf1/osf1_misc.c b/sys/alpha/osf1/osf1_misc.c
index 8a89891..0b74fab 100644
--- a/sys/alpha/osf1/osf1_misc.c
+++ b/sys/alpha/osf1/osf1_misc.c
@@ -1056,17 +1056,20 @@ osf1_setuid(td, uap)
 	struct proc *p;
 	int error;
 	uid_t uid;
+	struct uidinfo *uip;
 	struct ucred *newcred, *oldcred;
 
 	p = td->td_proc;
 	uid = SCARG(uap, uid);
 	newcred = crget();
+	uip = uifind(uid);
 	PROC_LOCK(p);
 	oldcred = p->p_ucred;
 
 	if ((error = suser_cred(p->p_ucred, PRISON_ROOT)) != 0 &&
 	    uid != oldcred->cr_ruid && uid != oldcred->cr_svuid) {
 		PROC_UNLOCK(p);
+		uifree(uip);
 		crfree(newcred);
 		return (error);
 	}
@@ -1074,7 +1077,7 @@ osf1_setuid(td, uap)
 	crcopy(newcred, oldcred);
 	if (error == 0) {
 		if (uid != oldcred->cr_ruid) {
-			change_ruid(newcred, uid);
+			change_ruid(newcred, uip);
 			setsugid(p);
 		}
 		if (oldcred->cr_svuid != uid) {
@@ -1083,11 +1086,12 @@ osf1_setuid(td, uap)
 		}
 	}
 	if (newcred->cr_uid != uid) {
-		change_euid(newcred, uid);
+		change_euid(newcred, uip);
 		setsugid(p);
 	}
 	p->p_ucred = newcred;
 	PROC_UNLOCK(p);
+	uifree(uip);
 	crfree(oldcred);
 	return (0);
 }