linux-kernel - [PATCH] ext4: Don't reduce symlink i

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Message-ID: <1553599.1715262072@warthog.procyon.org.uk>
Date: Thu, 09 May 2024 14:41:12 +0100
From: David Howells <dhowells@...hat.com>
To: Max Kellermann <max.kellermann@...os.com>, Jan Kara <jack@...e.com>
cc: dhowells@...hat.com, Christian Brauner <brauner@...nel.org>,
    linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
    linux-kernel@...r.kernel.org
Subject: [PATCH] ext4: Don't reduce symlink i_mode by umask if no ACL support

If CONFIG_EXT4_FS_POSIX_ACL=n then the fallback version of ext4_init_acl()
will mask off the umask bits from the new inode's i_mode.  This should not
be done if the inode is a symlink.  If CONFIG_EXT4_FS_POSIX_ACL=y, then we
go through posix_acl_create() instead which does the right thing with
symlinks.

Fix this by making the fallback version of ext4_init_acl() do nothing if
inode is a symlink.

Fixes: 484fd6c1de13 ("ext4: apply umask if ACL support is disabled")
Signed-off-by: David Howells <dhowells@...hat.com>
---
 fs/ext4/acl.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/acl.h b/fs/ext4/acl.h
index ef4c19e5f570..566625286442 100644
--- a/fs/ext4/acl.h
+++ b/fs/ext4/acl.h
@@ -71,7 +71,8 @@ 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();
+	if (!S_ISLNK(inode->i_mode))
+		inode->i_mode &= ~current_umask();
 
 	return 0;
 }