From 75fbe7eb99c3d20403c79c7e24a97997c424313a Mon Sep 17 00:00:00 2001
From: Ameer Hamza <ahamza@ixsystems.com>
Date: Wed, 23 Nov 2022 01:28:13 +0500
Subject: [PATCH] skip permission checks for extended attributes

zfs_zaccess_trivial() calls the generic_permission() to read
xattr attributes. This causes deadlock if called from
zpl_xattr_set_dir() context as xattr and the dent locks are
already held in this scenario. This commit skips the permissions
checks for extended attributes since the Linux VFS stack already
checks it before passing us the control.

Signed-off-by: Ameer Hamza <ahamza@ixsystems.com>
---
 module/os/linux/zfs/zfs_dir.c                                | 3 ---
 module/os/linux/zfs/zfs_vnops_os.c                           | 3 ++-
 module/os/linux/zfs/zpl_xattr.c                              | 2 +-
 tests/zfs-tests/tests/functional/acl/posix/posix_004_pos.ksh | 3 +++
 4 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/module/os/linux/zfs/zfs_dir.c b/module/os/linux/zfs/zfs_dir.c
index 82b32d1cc3..8ad5454b5a 100644
--- a/module/os/linux/zfs/zfs_dir.c
+++ b/module/os/linux/zfs/zfs_dir.c
@@ -1066,9 +1066,6 @@ zfs_make_xattrdir(znode_t *zp, vattr_t *vap, znode_t **xzpp, cred_t *cr)
 
 	*xzpp = NULL;
 
-	if ((error = zfs_zaccess(zp, ACE_WRITE_NAMED_ATTRS, 0, B_FALSE, cr)))
-		return (error);
-
 	if ((error = zfs_acl_ids_create(zp, IS_XATTR, vap, cr, NULL,
 	    &acl_ids)) != 0)
 		return (error);
diff --git a/module/os/linux/zfs/zfs_vnops_os.c b/module/os/linux/zfs/zfs_vnops_os.c
index 796a86c25a..ae0401e60e 100644
--- a/module/os/linux/zfs/zfs_vnops_os.c
+++ b/module/os/linux/zfs/zfs_vnops_os.c
@@ -579,6 +579,7 @@ zfs_create(znode_t *dzp, char *name, vattr_t *vap, int excl,
 	boolean_t	fuid_dirtied;
 	boolean_t	have_acl = B_FALSE;
 	boolean_t	waited = B_FALSE;
+	boolean_t	skip_acl = (flag & ATTR_NOACLCHECK) ? B_TRUE : B_FALSE;
 
 	/*
 	 * If we have an ephemeral id, ACL, or XVATTR then
@@ -651,7 +652,7 @@ top:
 		 * Create a new file object and update the directory
 		 * to reference it.
 		 */
-		if ((error = zfs_zaccess(dzp, ACE_ADD_FILE, 0, B_FALSE, cr))) {
+		if ((error = zfs_zaccess(dzp, ACE_ADD_FILE, 0, skip_acl, cr))) {
 			if (have_acl)
 				zfs_acl_ids_free(&acl_ids);
 			goto out;
diff --git a/module/os/linux/zfs/zpl_xattr.c b/module/os/linux/zfs/zpl_xattr.c
index bd5d5803fb..9d758d2d0e 100644
--- a/module/os/linux/zfs/zpl_xattr.c
+++ b/module/os/linux/zfs/zpl_xattr.c
@@ -496,7 +496,7 @@ zpl_xattr_set_dir(struct inode *ip, const char *name, const void *value,
 		vap->va_gid = crgetgid(cr);
 
 		error = -zfs_create(dxzp, (char *)name, vap, 0, 0644, &xzp,
-		    cr, 0, NULL);
+		    cr, ATTR_NOACLCHECK, NULL);
 		if (error)
 			goto out;
 	}
diff --git a/tests/zfs-tests/tests/functional/acl/posix/posix_004_pos.ksh b/tests/zfs-tests/tests/functional/acl/posix/posix_004_pos.ksh
index 6c6b592fbb..8aa2cf4960 100755
--- a/tests/zfs-tests/tests/functional/acl/posix/posix_004_pos.ksh
+++ b/tests/zfs-tests/tests/functional/acl/posix/posix_004_pos.ksh
@@ -35,6 +35,7 @@
 # STRATEGY:
 #	1. Prepare an appropriate ACL on the test directory
 #	2. Change the owner of the directory
+#	3. Reset and set the ACLs for test directory owned by the user
 #
 
 verify_runnable "both"
@@ -44,6 +45,8 @@ log_must setfacl -d -m u:$ZFS_ACL_STAFF1:rwx $TESTDIR
 log_must setfacl -b $TESTDIR
 
 log_must chown $ZFS_ACL_STAFF1 $TESTDIR
+log_must setfacl -b $TESTDIR
+log_must setfacl -d -m u:$ZFS_ACL_STAFF1:rwx $TESTDIR
 log_must chown 0 $TESTDIR
 
 log_pass "chown works with POSIX ACLs"