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[68.48.65.54]) by smtp.gmail.com with ESMTPSA id af79cd13be357-92ee5d5fc4dsm89983185a.40.2026.07.09.19.31.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jul 2026 19:31:45 -0700 (PDT) From: Michael Bommarito To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org Subject: Please consider 83f99de1b7c0 ("ext2: fix race between setxattr and write back") for 5.10.y, 5.15.y, and 6.1.y Date: Thu, 9 Jul 2026 22:31:42 -0400 Message-ID: <20260710023142.3748810-1-michael.bommarito@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Please consider the following already-mainlined fix for the stable series listed below. Upstream commit: 83f99de1b7c0dcfa42b211e5e40334b7ad786b36 Subject: ext2: fix race between setxattr and write back This is a stable option-2 request for an already-mainlined fix. The patch fixes a security-relevant bug pattern that remains present in the listed stable branches in my current review. Why this belongs in stable: ext2_xattr_set2 allocates a block via the reservation window concurrently with writeback (ext2_get_blocks), tripping rsv_window_dump BUG() in ext2_try_to_allocate_with_rsv (panic/DoS); fix absent in the checked stable branches and the unguarded reservation path plus reservation-using xattr allocation are still present there. Requested stable series: - 5.10.y - 5.15.y - 6.1.y Fresh stable check (2026-07-08): - 5.10.y: 738ac465e4e9 fix shape: absent; upstream diff: needs-adjustment - 5.15.y: c86c4726e7f0 fix shape: absent; upstream diff: needs-adjustment - 6.1.y: 090666d3cc90 fix shape: absent; upstream diff: needs-adjustment - 6.6.y and newer checked longterms already have the fixed shape The source-shape check looked for both the EXT2_ALLOC_NORESERVE xattr allocation call and the matching reservation guard in fs/ext2/balloc.c. Those are absent in the requested branches and present in the checked 6.6.y, 6.12.y, and 6.18.y branches. Backport note: The mechanical check above reports whether the upstream diff applies to each listed branch as-is. Branches marked needs-adjustment may need an equivalent stable backport rather than a straight cherry-pick. The current upstream diff fails in fs/ext2/xattr.c at the same hunk on 5.10.y, 5.15.y, and 6.1.y, so an adjusted backport is expected for all three requested series. Impact: a local user with write access to an already-mounted writable ext2 filesystem with user xattrs enabled can trigger a kernel BUG/oops through user.* xattr churn and writeback pressure. I do not have evidence for privilege escalation, code execution, or confidentiality/integrity impact; this is an availability issue. My current CVSS 3.1 estimate for that mounted-ext2 scope is 5.5. Direct-tracking exposure in my current review includes Debian 11, Debian 12, Amazon Linux 2023, and Android 13/14/15 GKI. Vendor trees that do not directly track the above stable branches need separate per-tree checks. Primary touched files: fs/ext2/balloc.c, fs/ext2/xattr.c No reproducer is included in this public stable request. I can provide additional details privately if needed.