2024-05-09 13:41:33

by David Howells

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 <[email protected]>
---
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;
}

2024-05-09 14:08:54

by David Howells

Subject: Re: [PATCH] ext4: Don't reduce symlink i_mode by umask if no ACL support

Miklos Szeredi <[email protected]> wrote:

> I think this should just be removed unconditionally, since the VFS now
> takes care of mode masking in vfs_prepare_mode().

That works for symlinks because the symlink path doesn't call it?

David

2024-05-09 14:10:25

by Miklos Szeredi

Subject: Re: [PATCH] ext4: Don't reduce symlink i_mode by umask if no ACL support

On Thu, 9 May 2024 at 16:08, David Howells <[email protected]> wrote:
>
> Miklos Szeredi <[email protected]> wrote:
>
> > I think this should just be removed unconditionally, since the VFS now
> > takes care of mode masking in vfs_prepare_mode().
>
> That works for symlinks because the symlink path doesn't call it?

Yep.

Thanks,
Miklos

2024-05-09 14:28:27

by Theodore Ts'o

Subject: Re: [PATCH] ext4: Don't reduce symlink i_mode by umask if no ACL support

On Thu, May 09, 2024 at 03:47:27PM +0200, Miklos Szeredi wrote:
> On Thu, 9 May 2024 at 15:41, David Howells <[email protected]> wrote:
>
> > 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();
>
> I think this should just be removed unconditionally, since the VFS now
> takes care of mode masking in vfs_prepare_mode().

The following is in the ext4 tree:

commit c77194965dd0dcc26f9c1671d2e74e4eb1248af5
Author: Max Kellermann <[email protected]>
Date: Fri Mar 15 15:29:56 2024 +0100

Revert "ext4: apply umask if ACL support is disabled"

This reverts commit 484fd6c1de13b336806a967908a927cc0356e312. The
commit caused a regression because now the umask was applied to
symlinks and the fix is unnecessary because the umask/O_TMPFILE bug
has been fixed somewhere else already.

Fixes: https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Max Kellermann <[email protected]>
Reviewed-by: Christian Brauner <[email protected]>
Tested-by: Michael Forney <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>