From: Al Viro <viro@zeniv.linux.org.uk>
To: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: linux-efi@vger.kernel.org, linux-fsdevel@vger.kernel.org,
"Ard Biesheuvel" <ardb@kernel.org>,
"Ryan Lee" <ryan.lee@canonical.com>,
"Malte Schröder" <malte.schroeder@tnxip.de>,
"Christian Brauner" <brauner@kernel.org>
Subject: Re: [PATCH] efivarfs: fix NULL dereference on resume
Date: Tue, 18 Mar 2025 03:37:38 +0000 [thread overview]
Message-ID: <20250318033738.GV2023217@ZenIV> (raw)
In-Reply-To: <3e998bf87638a442cbc6864cdcd3d8d9e08ce3e3.camel@HansenPartnership.com>
On Mon, Mar 17, 2025 at 11:06:01PM -0400, James Bottomley wrote:
> + /* ensure single superblock is alive and pin it */
> + if (!atomic_inc_not_zero(&s->s_active))
> + return NOTIFY_DONE;
> +
> pr_info("efivarfs: resyncing variable state\n");
>
> - /* O_NOATIME is required to prevent oops on NULL mnt */
> + path.dentry = sfi->sb->s_root;
> +
> + /*
> + * do not add SB_KERNMOUNT which a single superblock could
> + * expose to userspace and which also causes MNT_INTERNAL, see
> + * below
> + */
> + path.mnt = vfs_kern_mount(&efivarfs_type, 0,
> + efivarfs_type.name, NULL);
Umm... That's probably safe, but not as a long-term solution -
it's too intimately dependent upon fs/super.c internals.
The reasons why you can't run into ->s_umount deadlock here
are non-trivial...
next prev parent reply other threads:[~2025-03-18 3:37 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-18 3:06 [PATCH] efivarfs: fix NULL dereference on resume James Bottomley
2025-03-18 3:37 ` Al Viro [this message]
2025-03-18 7:04 ` Ard Biesheuvel
2025-03-18 7:49 ` Al Viro
2025-03-18 12:15 ` James Bottomley
2025-03-18 14:13 ` Christian Brauner
2025-03-18 14:52 ` James Bottomley
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