git: 7f4e724829e5 - main - jail: add a missing lock around an osd_jail_call().

[Jamie Gritton]

The branch main has been updated by jamie:

URL: https://cgit.FreeBSD.org/src/commit/?id=7f4e724829e556fc646056669c2af3551b7e8724

commit 7f4e724829e556fc646056669c2af3551b7e8724
Author:     Jamie Gritton <jamie at FreeBSD.org>
AuthorDate: 2020-12-27 04:49:30 +0000
Commit:     Jamie Gritton <jamie at FreeBSD.org>
CommitDate: 2020-12-27 04:49:30 +0000

    jail: add a missing lock around an osd_jail_call().
    
    allprison_lock should be at least held shared when jail OSD methods
    are called.  Add a shared lock around one such call where that wasn't
    the case.
    
    In another such call, change an exclusive lock grab to be shared in
    what is likely the more common case.
---
 sys/kern/kern_jail.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/sys/kern/kern_jail.c b/sys/kern/kern_jail.c
index a140b6f537d1..fb77cf87126d 100644
--- a/sys/kern/kern_jail.c
+++ b/sys/kern/kern_jail.c
@@ -2498,8 +2498,9 @@ do_jail_attach(struct thread *td, struct prison *pr)
 	VOP_UNLOCK(pr->pr_root);
  e_revert_osd:
 	/* Tell modules this thread is still in its old jail after all. */
+	sx_slock(&allprison_lock);
 	(void)osd_jail_call(td->td_ucred->cr_prison, PR_METHOD_ATTACH, td);
-	prison_deref(pr, PD_DEREF | PD_DEUREF);
+	prison_deref(pr, PD_DEREF | PD_DEUREF | PD_LIST_SLOCKED);
 	return (error);
 }
 
@@ -2687,8 +2688,13 @@ prison_deref(struct prison *pr, int flags)
 		 */
 		if (lasturef) {
 			if (!(flags & (PD_LIST_SLOCKED | PD_LIST_XLOCKED))) {
-				sx_xlock(&allprison_lock);
-				flags |= PD_LIST_XLOCKED;
+				if (ref > 1) {
+					sx_slock(&allprison_lock);
+					flags |= PD_LIST_SLOCKED;
+				} else {
+					sx_xlock(&allprison_lock);
+					flags |= PD_LIST_XLOCKED;
+				}
 			}
 			(void)osd_jail_call(pr, PR_METHOD_REMOVE, NULL);
 			mtx_lock(&pr->pr_mtx);