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Sun, 10 May 2026 07:38:35 -0700 (PDT) From: Zhang Cen To: Qu Wenruo Cc: Chris Mason , David Sterba , linux-btrfs@vger.kernel.org, zerocling0077@gmail.com, 2045gemini@gmail.com, Zhang Cen Subject: Re: [PATCH] btrfs: validate ROOT_BACKREF name before copying subvolume info Date: Sun, 10 May 2026 22:37:37 +0800 Message-Id: <20260510143737.3710790-1-rollkingzzc@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: <20260510074943.2644335-1-rollkingzzc@gmail.com> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Sun, May 10, 2026 at 04:18:00PM +0800, Qu Wenruo wrote: > The validation is too late. > > btrfs subvolume creation only accept BTRFS_SUBVOL_NAME_MAX + 1 (for the > terminating \0). > > This means a subvolume ref/backref should not have a name longer than > BTRFS_SUBVOL_NAME_MAX in the first place. > > Such independent checks should all be done inside tree-checker. Agreed, thanks for the review. I'll move the on-disk ROOT_REF/ROOT_BACKREF validation into tree-checker for v2 and cover both key types there. The v2 change will reject items smaller than struct btrfs_root_ref, reject records where name_len does not match the item payload, and reject names longer than BTRFS_SUBVOL_NAME_MAX. I'll keep the BTRFS_IOC_GET_SUBVOL_INFO-side BTRFS_VOL_NAME_MAX check only as the local guard for its fixed-size UAPI output buffer before copying the already validated name. Thanks, Zhang