[PATCH] fs/ext4/acl: apply umask if ACL support is disabled

From: Max Kellermann <max.kellermann@ionos.com>
To: "Theodore Ts'o" <tytso@mit.edu>,
	Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Max Kellermann <max.kellermann@ionos.com>,
	"J . Bruce Fields" <bfields@redhat.com>,
	stable@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH] fs/ext4/acl: apply umask if ACL support is disabled
Date: Tue, 19 Sep 2023 10:18:23 +0200	[thread overview]
Message-ID: <20230919081824.1096619-1-max.kellermann@ionos.com> (raw)

The function ext4_init_acl() calls posix_acl_create() which is
responsible for applying the umask.  But without
CONFIG_EXT4_FS_POSIX_ACL, ext4_init_acl() is an empty inline function,
and nobody applies the umask.

This fixes a bug which causes the umask to be ignored with O_TMPFILE
on ext4:

 https://github.com/MusicPlayerDaemon/MPD/issues/558
 https://bugs.gentoo.org/show_bug.cgi?id=686142#c3
 https://bugzilla.kernel.org/show_bug.cgi?id=203625

Reviewed-by: J. Bruce Fields <bfields@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
---
 fs/ext4/acl.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/ext4/acl.h b/fs/ext4/acl.h
index 0c5a79c3b5d4..ef4c19e5f570 100644
--- a/fs/ext4/acl.h
+++ b/fs/ext4/acl.h
@@ -68,6 +68,11 @@ extern int ext4_init_acl(handle_t *, struct inode *, struct inode *);
 static inline int
 ext4_init_acl(handle_t *handle, struct inode *inode, struct inode *dir)
 {
+	/* usually, the umask is applied by posix_acl_create(), but if
+	   ext4 ACL support is disabled at compile time, we need to do
+	   it here, because posix_acl_create() will never be called */
+	inode->i_mode &= ~current_umask();
+
 	return 0;
 }
 #endif  /* CONFIG_EXT4_FS_POSIX_ACL */
-- 
2.39.2

