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Fri, 25 Jul 2025 00:47:19 -0700 (PDT) Date: Fri, 25 Jul 2025 00:47:19 -0700 In-Reply-To: <686db3ea.050a0220.1ffab7.0028.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <68833687.a00a0220.2f88df.0040.GAE@google.com> Subject: Forwarded: Re: [syzbot] [rdma?] KASAN: slab-use-after-free Read in ucma_create_uevent From: syzbot To: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org. *** Subject: Re: [syzbot] [rdma?] KASAN: slab-use-after-free Read in ucma_creat= e_uevent Author: lizhi.xu@windriver.com #syz test diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c index 6e700b974033..89c444c6f317 100644 --- a/drivers/infiniband/core/ucma.c +++ b/drivers/infiniband/core/ucma.c @@ -109,6 +109,7 @@ struct ucma_multicast { u8 join_state; struct list_head list; struct sockaddr_storage addr; + atomic_t ref; }; =20 struct ucma_event { @@ -257,6 +258,12 @@ static void ucma_copy_ud_event(struct ib_device *devic= e, dst->qkey =3D src->qkey; } =20 +static void ucma_put_mc(struct ucma_multicast *mc) +{ + if (mc && atomic_dec_and_test(&mc->ref)) + kfree(mc); +} + static struct ucma_event *ucma_create_uevent(struct ucma_context *ctx, struct rdma_cm_event *event) { @@ -274,6 +281,7 @@ static struct ucma_event *ucma_create_uevent(struct ucm= a_context *ctx, event->param.ud.private_data; uevent->resp.uid =3D uevent->mc->uid; uevent->resp.id =3D uevent->mc->id; + ucma_put_mc(uevent->mc); break; default: uevent->resp.uid =3D ctx->uid; @@ -1471,6 +1479,7 @@ static ssize_t ucma_process_join(struct ucma_file *fi= le, mc->ctx =3D ctx; mc->join_state =3D join_state; mc->uid =3D cmd->uid; + atomic_set(&mc->ref, 1); memcpy(&mc->addr, addr, cmd->addr_size); =20 xa_lock(&multicast_table); @@ -1489,6 +1498,7 @@ static ssize_t ucma_process_join(struct ucma_file *fi= le, mutex_unlock(&ctx->mutex); if (ret) goto err_xa_erase; + atomic_inc(&mc->ref); =20 resp.id =3D mc->id; if (copy_to_user(u64_to_user_ptr(cmd->response), @@ -1513,7 +1523,7 @@ static ssize_t ucma_process_join(struct ucma_file *fi= le, __xa_erase(&multicast_table, mc->id); err_free_mc: xa_unlock(&multicast_table); - kfree(mc); + ucma_put_mc(mc); err_put_ctx: ucma_put_ctx(ctx); return ret;