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[178.84.201.199]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c5095b5ac2asm211518966b.55.2026.11.14.04.19.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Nov 2026 04:19:56 -0800 (PST) Date: Sat, 14 Nov 2026 13:19:56 +0100 From: Amir Goldstein To: Christian Brauner Cc: Jan Kara , Shakeel Butt , Alexander Viro , Jens Axboe , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, io-uring@vger.kernel.org, Christoph Hellwig , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-unionfs@vger.kernel.org, bpf@vger.kernel.org, linux-nfs@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 10/12] ovl: take freeze protection when storing the uuid Message-ID: References: <20261114-work-fs-frozen_writes-v1-0-f5ae61c898b1@kernel.org> <20261114-work-fs-frozen_writes-v1-10-f5ae61c898b1@kernel.org> X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261114-work-fs-frozen_writes-v1-10-f5ae61c898b1@kernel.org> On Sat, Nov 14, 2026 at 11:47:17AM +0100, Christian Brauner wrote: > ovl_init_uuid_xattr() stores the persistent uuid in an xattr on the > upper root. That happens after ovl_make_workdir() dropped its write > access to the upper mount and before ovl_get_indexdir() takes it > again. So a freeze of the upper filesystem that lands in between lets > the mount modify a frozen filesystem. > > Take write access to the upper mount around the xattr update. > > Fixes: d9544c1b0d9e ("ovl: store persistent uuid/fsid with uuid=on") > Cc: stable@vger.kernel.org > Signed-off-by: Christian Brauner (Amutable) Reviewed-by: Amir Goldstein Thanks, Amir. > --- > fs/overlayfs/util.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c > index 521717209b2e4..67aa7b71e9c83 100644 > --- a/fs/overlayfs/util.c > +++ b/fs/overlayfs/util.c > @@ -829,8 +829,12 @@ bool ovl_init_uuid_xattr(struct super_block *sb, struct ovl_fs *ofs, > > /* Try to store persistent uuid */ > set = true; > - res = ovl_setxattr(ofs, upperpath->dentry, OVL_XATTR_UUID, uuid.b, > - UUID_SIZE); > + res = mnt_want_write(ovl_upper_mnt(ofs)); > + if (!res) { > + res = ovl_setxattr(ofs, upperpath->dentry, OVL_XATTR_UUID, > + uuid.b, UUID_SIZE); > + mnt_drop_write(ovl_upper_mnt(ofs)); > + } > if (res) > goto fail; > > > -- > 2.53.0 >