linux-kernel - Re: [PATCH] nfs: Fix potential posix_acl refcnt leak in nfs3_set

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Date:   Mon, 20 Apr 2020 14:51:41 +0200
From:   Andreas Gruenbacher <agruenba@...hat.com>
To:     Trond Myklebust <trondmy@...merspace.com>,
        "akpm@...l.org" <akpm@...l.org>,
        "xiyuyang19@...an.edu.cn" <xiyuyang19@...an.edu.cn>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "anna.schumaker@...app.com" <anna.schumaker@...app.com>,
        "okir@...e.de" <okir@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Andreas Gruenbacher <agruenba@...hat.com>,
        "tanxin.ctf@...il.com" <tanxin.ctf@...il.com>,
        "yuanxzhang@...an.edu.cn" <yuanxzhang@...an.edu.cn>,
        "kjlu@....edu" <kjlu@....edu>
Subject: Re: [PATCH] nfs: Fix potential posix_acl refcnt leak in nfs3_set_acl

Am Mo., 20. Apr. 2020 um 14:15 Uhr schrieb Trond Myklebust <trondmy@...merspace.com>:
> I don't really see any alternative to adding a 'dfalloc' to track the
> allocated dfacl separately.

Something like the attached patch should work as well.

Thanks,
Andreas

---
 fs/nfs/nfs3acl.c | 32 ++++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c
index c5c3fc6e6c60..f1581f11c220 100644
--- a/fs/nfs/nfs3acl.c
+++ b/fs/nfs/nfs3acl.c
@@ -253,37 +253,41 @@ int nfs3_proc_setacls(struct inode *inode, struct posix_acl *acl,
 
 int nfs3_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 {
-	struct posix_acl *alloc = NULL, *dfacl = NULL;
+	struct posix_acl *orig = acl, *dfacl = NULL;
 	int status;
 
 	if (S_ISDIR(inode->i_mode)) {
 		switch(type) {
 		case ACL_TYPE_ACCESS:
-			alloc = dfacl = get_acl(inode, ACL_TYPE_DEFAULT);
-			if (IS_ERR(alloc))
-				goto fail;
+			dfacl = get_acl(inode, ACL_TYPE_DEFAULT);
+			status = PTR_ERR(dfacl);
+			if (IS_ERR(dfacl))
+				goto out;
 			break;
 
 		case ACL_TYPE_DEFAULT:
 			dfacl = acl;
-			alloc = acl = get_acl(inode, ACL_TYPE_ACCESS);
-			if (IS_ERR(alloc))
-				goto fail;
+			acl = get_acl(inode, ACL_TYPE_ACCESS);
+			status = PTR_ERR(acl);
+			if (IS_ERR(acl))
+				goto out;
 			break;
 		}
 	}
 
 	if (acl == NULL) {
-		alloc = acl = posix_acl_from_mode(inode->i_mode, GFP_KERNEL);
-		if (IS_ERR(alloc))
-			goto fail;
+		acl = posix_acl_from_mode(inode->i_mode, GFP_KERNEL);
+		status = PTR_ERR(acl);
+		if (IS_ERR(acl))
+			goto out;
 	}
 	status = __nfs3_proc_setacls(inode, acl, dfacl);
-	posix_acl_release(alloc);
+out:
+	if (acl != orig)
+		posix_acl_release(acl);
+	if (dfacl != orig)
+		posix_acl_release(dfacl);
 	return status;
-
-fail:
-	return PTR_ERR(alloc);
 }
 
 const struct xattr_handler *nfs3_xattr_handlers[] = {

base-commit: ae83d0b416db002fe95601e7f97f64b59514d936
-- 
2.25.3