From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Yuan Tan <yuantan098@gmail.com>,
	Zhengchuan Liang <zcliangcn@gmail.com>,
	Xin Liu <bird@lzu.edu.cn>,
	Douya Le <ldy3087146292@gmail.com>,
	Ren Wei <n05ec@lzu.edu.cn>,
	Ilya Dryomov <idryomov@gmail.com>
Subject: [PATCH 6.18 519/675] libceph: reject zero bucket types in crush_decode
Date: Thu, 30 Jul 2026 16:14:09 +0200
Message-ID: <20260730141456.169303581@linuxfoundation.org>
In-Reply-To: <20260730141445.110192266@linuxfoundation.org>
References: <20260730141445.110192266@linuxfoundation.org>
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6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Douya Le <ldy3087146292@gmail.com>

commit 05f90284223381005d6bcddab3fda4a97f9c3401 upstream.

CRUSH bucket type 0 is reserved for devices.  The mapper relies on
that invariant and uses type 0 to identify leaf devices.

If crush_decode() accepts a bucket with type 0, a malformed CRUSH map
can make the mapper treat a negative bucket ID as a device and pass it
to is_out(), which then indexes the OSD weight array with a negative
value.

Reject zero bucket types while decoding the CRUSH map so the invalid
state never reaches the mapper.

Cc: stable@vger.kernel.org
Fixes: f24e9980eb86 ("ceph: OSD client")
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Zhengchuan Liang <zcliangcn@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Assisted-by: Codex:GPT-5.4
Signed-off-by: Douya Le <ldy3087146292@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ceph/osdmap.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/ceph/osdmap.c
+++ b/net/ceph/osdmap.c
@@ -520,6 +520,8 @@ static struct crush_map *crush_decode(vo
 		ceph_decode_need(p, end, 4*sizeof(u32), bad);
 		b->id = ceph_decode_32(p);
 		b->type = ceph_decode_16(p);
+		if (b->type == 0)
+			goto bad;
 		b->alg = ceph_decode_8(p);
 		if (b->alg != alg) {
 			b->alg = 0;