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

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Date:   Tue, 19 Sep 2023 10:18:23 +0200
From:   Max Kellermann <max.kellermann@...os.com>
To:     "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>
Cc:     Max Kellermann <max.kellermann@...os.com>,
        "J . Bruce Fields" <bfields@...hat.com>, stable@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] fs/ext4/acl: apply umask if ACL support is disabled

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@...hat.com>
Cc: stable@...r.kernel.org
Signed-off-by: Max Kellermann <max.kellermann@...os.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