From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 056D3404BFF for ; Sat, 15 Aug 2026 12:33:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786797222; cv=none; b=E67tGNYtJHI86TqS2pNGPnle3RQmuimYEFhCKzl2CuOxbas/itpLiNngDes/zLdTdKOCxaXgGhph/GWWNh2tgWfK+U+xW4u3akR/uETWWADZejsv3+ih+qIwQDJaqn+M6LJmQjtlFEu3NfzyXYmzd/UFGF8Rk9+Ie5JsWgCTtZw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786797222; c=relaxed/simple; bh=G4eVQszQ9Ny9Yzt84GCPQV5/3JuFr9GWG7qYatcmeJM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=nmEhHnAfw87OdNNsWkzaPtlfjM1Uxc9f+QsD9o9VnRNJLLhbfrhWvGqbpqn+mz41aaPo6Fm9kK/vTgceZg2cP6F7pjZQqc6nv6vf1CmOJ2AUVdhpXWXVdmaqogi8pILeU2STAIqbrnWNWfQkuyDCiK9z5K1QNgRHBSx1BRmgOmU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=dFMIWuma; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="dFMIWuma" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5C2841F000E9; Sat, 15 Aug 2026 12:33:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786797220; bh=SLUUX98g0E0HsEwsQlEfr4cmTHypTj5Gnh5Jy5MT68A=; h=From:To:Cc:Subject:Date:Reply-To; b=dFMIWumaSKkIRm409pHaD7sj5aOLRnI6cOoAm84hFAhv1B/WS18bTHhNm95wotPWN ZBQZ8oMDwWSfzmZywApYUUxw0ib5xE5sM4URbnFtKZvRkRfucowos6Bll54U/2IyNF pv8IhoAKW8vK85PXIIxs6cye1dwaE9Lyf3leh8AY= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-74571: btrfs: skip global block reserve accounting for rescue mounts Date: Sat, 15 Aug 2026 21:27:32 +0900 Message-ID: <2026081554-CVE-2026-74571-b7b1@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3179; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=FCmnY9wvxDy1s6Rub17CIZBLQboRRXf23V4TEJW1sdY=; b=owGbwMvMwCRo6H6F97bub03G02pJDFkNUZdYp3TO+Knj88Vk5+X3r7VDd0+MmTv3G4/xjaN9s c+Oz1YI7ohlYRBkYpAVU2T5so3n6P6KQ4pehranYeawMoEMYeDiFICJpPkyLGhO3vryddcsprv6 dfxlW7dMYPAOuc+wYN/7FT1Bv/4cF1xz4LyQ2KnWP0a+VgA= X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: btrfs: skip global block reserve accounting for rescue mounts [BUG] Mounting with rescue=ibadroots after corrupting the block group tree root triggers a NULL pointer dereference: BUG: kernel NULL pointer dereference, address: 0000000000000100 RIP: 0010:btrfs_update_global_block_rsv+0x9d/0x1c0 [btrfs] Call Trace: fill_dummy_bgs+0xd4/0x120 [btrfs] open_ctree+0xc6e/0x1ca0 [btrfs] btrfs_get_tree+0x50d/0xa40 [btrfs] The same crash occurs with a corrupted raid stripe tree root, via btrfs_read_block_groups() instead of fill_dummy_bgs(). [CAUSE] With rescue=ibadroots, btrfs_read_roots() allows the mount to continue when either root cannot be read, leaving the corresponding root pointer NULL while its on-disk feature bit remains set. btrfs_update_global_block_rsv() then dereferences the missing root based on the feature bit alone. [FIX] Rescue mounts are fully read-only and cannot start transactions, so the global reserve is never consumed. Under btrfs_is_full_ro(), mark the reserve as full and return before performing the accounting. And since we need to check if the fs is mount fully RO, export fs_is_full_ro() as btrfs_is_full_ro(), and move it to fs.h. [ Squash the fs_is_full_ro() export commit into this one. ] The Linux kernel CVE team has assigned CVE-2026-74571 to this issue. Affected and fixed versions =========================== Issue introduced in 6.5 with commit 8dbfc14fc736eb701089aff09645c3d4ad3decb1 and fixed in 7.1.8 with commit 076349e4c8d11f6b58c4549976a513b2b4dc6df2 Issue introduced in 6.5 with commit 8dbfc14fc736eb701089aff09645c3d4ad3decb1 and fixed in 7.2-rc6 with commit 51a0e8399858621442807a26057bcd1cd3ced046 Issue introduced in 6.1.43 with commit cbec34d3021d47007a0334c634f7053dbaf93d02 Issue introduced in 6.4.8 with commit 1e8087589b5cf6fa17adaf57b64cf1656d77dfec Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-74571 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/btrfs/block-rsv.c fs/btrfs/disk-io.c fs/btrfs/fs.h Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/076349e4c8d11f6b58c4549976a513b2b4dc6df2 https://git.kernel.org/stable/c/51a0e8399858621442807a26057bcd1cd3ced046