linux-kernel - Re: [PATCH] ovl: fix UAF in ovl_dentry_update_reval by moving dput() in ovl_link

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Message-ID: <20250219-erlitt-berappen-a4821fba4a83@brauner>
Date: Wed, 19 Feb 2025 18:07:05 +0100
From: Christian Brauner <brauner@...nel.org>
To: Vasiliy Kovalev <kovalev@...linux.org>
Cc: Christian Brauner <brauner@...nel.org>,
	linux-kernel@...r.kernel.org,
	lvc-project@...uxtesting.org,
	syzbot+316db8a1191938280eb6@...kaller.appspotmail.com,
	Miklos Szeredi <miklos@...redi.hu>,
	Amir Goldstein <amir73il@...il.com>,
	Gao Xiang <xiang@...nel.org>,
	linux-unionfs@...r.kernel.org
Subject: Re: [PATCH] ovl: fix UAF in ovl_dentry_update_reval by moving dput() in ovl_link_up

On Sat, 15 Feb 2025 00:51:48 +0300, Vasiliy Kovalev wrote:
> The issue was caused by dput(upper) being called before
> ovl_dentry_update_reval(), while upper->d_flags was still
> accessed in ovl_dentry_remote().
> 
> Move dput(upper) after its last use to prevent use-after-free.
> 
> BUG: KASAN: slab-use-after-free in ovl_dentry_remote fs/overlayfs/util.c:162 [inline]
> BUG: KASAN: slab-use-after-free in ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167
> 
> [...]

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[1/1] ovl: fix UAF in ovl_dentry_update_reval by moving dput() in ovl_link_up
      https://git.kernel.org/vfs/vfs/c/c84e125fff26