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 8B3482E2EEE; Tue, 25 Aug 2026 23:16:04 +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=1787699765; cv=none; b=fZLDpIyWrPUyk+W1HCBSzcPUq/WAZOptutgbM+dMBRLR8jcBdfDI7dTf+YfkuHTpKiHdPMEHY3oUooSL376SgbF1Amzayz9i5/zeUQoeYoqRR1e4/0+hbOjcsHp6v6juHiwWwTBvbl+Sn4jt47IFIhSKU5Nb7fuGHAjQckhTAWQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787699765; c=relaxed/simple; bh=yXPRHTpNE/+r66oOJ+ybxt/YZRDn7LfNAZ1LzkF10I0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=NH3rbeV+jz+D27XKJQBf+uDXEi4EzqF8gfAftUtJowGKeb53GQhmIuMNaX4HCnP+FSsdRbyuMB+6tfV2bdjSHZB8YYxLNXxceD0lK16qeYZHc343oaIhAPxG/9Ue7dTGuIkn0W0hJ4Be/CrbdjPtlja4/qYks5z4wBBtsPtvOjk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AAeDkljO; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AAeDkljO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CA5021F000E9; Tue, 25 Aug 2026 23:16:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787699764; bh=/cNmmNvhGlkxS7SZv8G19FI0tngiieRaSNNGyFvAoN8=; h=Subject:From:To:Cc:Date:In-Reply-To:References; b=AAeDkljOs34jOG2uw25vckPNe9JYWAino/q7dBjlAZtrOwBkvXxStswpwzSBXETrg YCsBeMyPRBJRwDKq+2WK9RjZfPYPLqD66PvwK0vYGy8pJ6hi4NtFjxKYdzBMogIByO aeXMY7tLL3ey3YC0m17co/MapgPSd8NqSCQU2D0sNwJHuu3YJ/kUV6cPZB+0MIIxyS HfYRsHkaqk9V3xvmL/5VQAXFOxUTUqkW30OqT5jZd9NRqCiXepAZkfxP/CyKcrphmg BCulmzTO8VDpggeiBL5dfS815XGqsFQBdqEQN97LY9lboiVAo2mCY98p1C3ciUk6dB x4nvXrBBCXUtg== Message-ID: <9898c771fb10d2a9b774f6ec4c7c94bc7b0129f7.camel@kernel.org> Subject: Re: [PATCH v2 net] net/rds: fix out-of-bounds write in rds_conn_peer_gen_update() From: Allison Henderson To: pamoutaf Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, netdev@vger.kernel.org, linux-rdma@vger.kernel.org, rds-devel@oss.oracle.com, linux-kernel@vger.kernel.org Date: Tue, 25 Aug 2026 16:16:03 -0700 In-Reply-To: <20260825120132.51636-1-pamoutafpro@gmail.com> References: <20260825120132.51636-1-pamoutafpro@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.52.3-0ubuntu1.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2026-08-25 at 13:01 +0100, pamoutaf wrote: > From: Paula Moutafian >=20 > rds_conn_peer_gen_update(), rds_start_mprds() and rds_check_all_paths() > all iterate conn->c_path[] up to RDS_MPATH_WORKERS (8) or conn->c_npaths, > but c_path is allocated with only >=20 > npaths =3D (trans->t_mp_capable ? RDS_MPATH_WORKERS : 1) >=20 > entries in __rds_conn_create() (net/rds/connection.c). Only the TCP > transport sets t_mp_capable, so for the IB/RDMA transport (and the loop > transport) exactly one rds_conn_path is allocated. >=20 > c_npaths is derived from the peer via the RDS_EXTHDR_NPATHS handshake > extension header and is only clamped to RDS_MPATH_WORKERS, never to the > transport's actual allocation. A remote peer on an RDS/IB (RoCE) fabric > can therefore complete the unauthenticated handshake and, by sending a > second RDS_EXTHDR_GEN_NUM with a changed generation number, drive > rds_conn_peer_gen_update() to walk c_path[1..7] past the end of a > one-element allocation -- taking cp_lock, writing cp_next_tx_seq / > cp_next_rx_seq and walking cp_retrans on neighbouring slab objects. > rds_start_mprds() and rds_check_all_paths() are reachable the same way > via a peer-supplied c_npaths > 1; note rds_check_all_paths() is a > do/while and dereferences c_path[0] before testing the bound. >=20 > Reproduced against an unmodified 7.2.0 KASAN build, triggered from a > hand-rolled RDS/IB peer completing the handshake and sending two probes > with differing RDS_EXTHDR_GEN_NUM: >=20 > BUG: KASAN: slab-out-of-bounds in do_raw_spin_lock+0x55/0x9a > Write of size 4 at addr ff1100000425a624 by task ksoftirqd/0/13 > Call Trace: > do_raw_spin_lock+0x55/0x9a > _raw_spin_lock_irqsave+0x12/0x18 > rds_recv_hs_exthdrs+0x34a/0x52a > rds_recv_incoming+0x5a8/0xb33 > rds_ib_recv_cqe_handler+0xda1/0x12b6 > poll_rcq+0x8e/0xb1 > rds_ib_tasklet_fn_recv+0x1c4/0x348 > Allocated by task 10: > __rds_conn_create+0x5b3/0x168f > rds_conn_create+0x18/0x1b > rds_ib_cm_handle_connect+0x486/0xa35 > The buggy address is located 44 bytes to the right of > allocated 504-byte region, cache kmalloc-512 >=20 > The corrupted neighbour's cp_retrans.next is then dereferenced on the > next line, producing a fatal GPF (RIP: rds_recv_hs_exthdrs+0x3ba/0x52a, > KASAN: null-ptr-deref) -- a crash, not merely a detected access. >=20 > Fix conn->c_npaths at the source instead of guarding every reader: in > rds_recv_hs_exthdrs() (net/rds/recv.c), clamp the peer-supplied > RDS_EXTHDR_NPATHS value to the transport's actual per-connection > allocation rather than to the fixed RDS_MPATH_WORKERS ceiling. c_npaths > can then never exceed the number of rds_conn_path entries > __rds_conn_create() allocated, which takes care of rds_start_mprds() > and rds_check_all_paths() -- both already bound their loops by > conn->c_npaths -- with no change at either call site. >=20 > rds_conn_peer_gen_update() is different: its loop is bound by the fixed > RDS_MPATH_WORKERS constant, not by conn->c_npaths, so the c_npaths fix > above does not reach it. It still needs its own bound, computed the same > way as the allocation site and mirroring the sibling pattern already used > in rds_conn_destroy() (net/rds/connection.c). >=20 > rds_conn_peer_gen_update() and rds_start_mprds() (net/rds/recv.c) were > both correct when written, with c_path still a fixed > RDS_MPATH_WORKERS-element array: >=20 > commit 905dd4184e07 ("RDS: TCP: Track peer's connection generation number= ") > commit 5916e2c1554f ("RDS: TCP: Enable multipath RDS for TCP") >=20 > They became wrong when the allocation was made conditional on > t_mp_capable without updating either loop or the RDS_EXTHDR_NPATHS clamp: >=20 > commit 840df162b3eb ("rds: reduce memory footprint for RDS when transport= is RDMA") >=20 > rds_check_all_paths() (net/rds/connection.c) is unrelated to that > regression: it was added new, three years later, and was unbounded > from the moment it was written, but is fixed by the same c_npaths clamp: >=20 > commit 9ef845f894c9 ("rds: If one path needs re-connection, check all and= re-connect") >=20 > Fixes: 840df162b3eb ("rds: reduce memory footprint for RDS when transport= is RDMA") > Fixes: 9ef845f894c9 ("rds: If one path needs re-connection, check all and= re-connect") > Cc: stable@vger.kernel.org > Assisted-by: Bynario AI > Signed-off-by: Paula Moutafian Ok, this looks good to me. Thanks Paula! Reviewed-by: Allison Henderson > --- > v2: > - Per Allison Henderson's review, clamp conn->c_npaths itself at the > point it is set from the peer's RDS_EXTHDR_NPATHS in > rds_recv_hs_exthdrs(), instead of adding a second bound check at > each of its readers. This covers rds_start_mprds() and > rds_check_all_paths() with no further change at either site; > net/rds/connection.c is unchanged from v1. > - rds_conn_peer_gen_update()'s loop is bound by RDS_MPATH_WORKERS > directly, not by conn->c_npaths, so it is unaffected by the above > and keeps its own bound from v1. >=20 > [v1] https://lore.kernel.org/netdev/213829b7380f1fe12aed2f2ae9ba33c2870ad= dd5.camel@kernel.org/T/#t >=20 > net/rds/recv.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) >=20 > diff --git a/net/rds/recv.c b/net/rds/recv.c > index cf3884d87931..c7f575bad91c 100644 > --- a/net/rds/recv.c > +++ b/net/rds/recv.c > @@ -133,15 +133,16 @@ static void rds_recv_rcvbuf_delta(struct rds_sock *= rs, struct sock *sk, > static void rds_conn_peer_gen_update(struct rds_connection *conn, > u32 peer_gen_num) > { > - int i; > + int npaths =3D (conn->c_trans->t_mp_capable ? RDS_MPATH_WORKERS : 1); > struct rds_message *rm, *tmp; > unsigned long flags; > + int i; > =20 > WARN_ON(conn->c_trans->t_type !=3D RDS_TRANS_TCP); > if (peer_gen_num !=3D 0) { > if (conn->c_peer_gen_num !=3D 0 && > peer_gen_num !=3D conn->c_peer_gen_num) { > - for (i =3D 0; i < RDS_MPATH_WORKERS; i++) { > + for (i =3D 0; i < npaths; i++) { > struct rds_conn_path *cp; > =20 > cp =3D &conn->c_path[i]; > @@ -210,6 +211,7 @@ static void rds_recv_hs_exthdrs(struct rds_header *hd= r, > u32 new_peer_gen_num =3D 0; > int new_npaths; > bool fan_out; > + int npaths =3D (conn->c_trans->t_mp_capable ? RDS_MPATH_WORKERS : 1); > =20 > new_npaths =3D conn->c_npaths; > =20 > @@ -221,7 +223,7 @@ static void rds_recv_hs_exthdrs(struct rds_header *hd= r, > /* Process extension header here */ > switch (type) { > case RDS_EXTHDR_NPATHS: > - new_npaths =3D min_t(int, RDS_MPATH_WORKERS, > + new_npaths =3D min_t(int, npaths, > be16_to_cpu(buffer.rds_npaths)); > break; > case RDS_EXTHDR_GEN_NUM: >=20 > base-commit: 564973a259ec76f2dad0853420e7034cc43994c4