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([103.172.183.54]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2aece7ee1d8sm16742135ad.55.2026.03.13.02.19.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Mar 2026 02:19:32 -0700 (PDT) From: ZhengYuan Huang To: dsterba@suse.com, clm@fb.com Cc: wqu@suse.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, r33s3n6@gmail.com, zzzccc427@gmail.com, ZhengYuan Huang Subject: [PATCH v2 0/2] btrfs: verify cached extent buffers against tree parent checks Date: Fri, 13 Mar 2026 17:19:22 +0800 Message-ID: <20260313091924.570554-1-gality369@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This series fixes a btrfs crash caused by reusing a cached extent buffer without re-running the caller supplied tree-parent verification. The problem happens when a tree block is first read and validated with one expected level, then later looked up again through a path that derives a different expected level from corrupted metadata. If the extent buffer is already marked EXTENT_BUFFER_UPTODATE, the cached-hit path returns it without re-validating the supplied btrfs_tree_parent_check. This can allow an inconsistent btrfs_root to be constructed and later lead to a null-ptr-deref during backref walking. Patch 1/2 is a preparatory change that extends btrfs_buffer_uptodate() to support tree-parent verification on cached buffers. Patch 2/2 uses that support on the cached-hit path and contains the actual fix. Together, these changes make cache hits and fresh reads follow the same tree-parent verification rules, turning the corruption into a read failure instead of constructing an inconsistent root object and crashing later. For reference, a more detailed analysis of the trigger path is available at: https://lore.kernel.org/all/CAOmEq9U14a=pwN_dw2M70gfujhMKki434cfmegoxcyUpkYs5bQ@mail.gmail.com/ Changes since v1: - drop the adhoc root-specific consistency check in read_tree_root_path() - move the validation into the cached-hit path as suggested by Qu Wenruo - extend btrfs_buffer_uptodate() with an optional tree-parent check - make read_tree_root_path() pass its check when validating a cached root ZhengYuan Huang (2): btrfs: add tree parent check to btrfs_buffer_uptodate() btrfs: revalidate cached tree blocks on the uptodate path fs/btrfs/ctree.c | 2 +- fs/btrfs/disk-io.c | 18 ++++++++++++++---- fs/btrfs/disk-io.h | 3 ++- fs/btrfs/extent-tree.c | 2 +- fs/btrfs/extent_io.c | 12 ++++++++++-- fs/btrfs/tree-log.c | 2 +- 6 files changed, 29 insertions(+), 10 deletions(-) -- 2.43.0