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([2405:4802:1d38:5c70:dfd9:c41e:7c9b:c69]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2dd2cfc300bsm24585045ad.47.2026.09.12.09.34.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 12 Sep 2026 09:34:28 -0700 (PDT) From: Nguyen Ngoc Thang To: Dave Kleikamp Cc: jfs-discussion@lists.sourceforge.net, linux-kernel@vger.kernel.org, syzbot+dcea2548c903300a400e@syzkaller.appspotmail.com, Nguyen Ngoc Thang Subject: [PATCH] jfs: return -ENOSPC instead of BUG() on corrupted dmap tree in dbFindLeaf Date: Sat, 12 Sep 2026 23:34:22 +0700 Message-ID: <20260912163422.80989-1-ngocthang2710.1999@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: quoted-printable Content-Type: text/plain; charset="utf-8" dbFindLeaf() trusts the on-disk dmtree summary values: the root level says free space exists, then it searches each level's 4 children for one that actually provides it. A corrupted (e.g. crafted/fuzzed) JFS image can have a parent claim space that none of its children provide, which is neither validated on mount nor recoverable here -- it used to hit assert(n < 4), i.e. BUG(), crashing the kernel. Treat it the same way as the two existing sanity checks in this function and return -ENOSPC instead. Reported-by: syzbot+dcea2548c903300a400e@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Ddcea2548c903300a400e Signed-off-by: Nguyen Ngoc Thang --- fs/jfs/jfs_dmap.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c index a841cf21da7d..079765450bb2 100644 --- a/fs/jfs/jfs_dmap.c +++ b/fs/jfs/jfs_dmap.c @@ -3065,9 +3065,12 @@ static int dbFindLeaf(dmtree_t *tp, int l2nb, int *l= eafidx, bool is_ctl) } =20 /* better have found something since the higher - * levels of the tree said it was here. + * levels of the tree said it was here. A corrupted tree + * can claim free space at a level that no child actually + * provides. */ - assert(n < 4); + if (n =3D=3D 4) + return -ENOSPC; } if (le32_to_cpu(tp->dmt_leafidx) >=3D max_idx) return -ENOSPC; --=20 2.43.0