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Sat, 09 May 2026 01:42:42 -0700 (PDT) From: pomzm67@gmail.com To: security@kernel.org Cc: selvin.xavier@broadcom.com, kalesh-anakkur.purayil@broadcom.com, jgg@ziepe.ca, leon@kernel.org, eddie.wai@broadcom.com, somnath.kotur@broadcom.com, sriharsha.basavapatna@broadcom.com, devesh.sharma@broadcom.com, dledford@redhat.com, gregkh@linuxfoundation.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, Lord Ulf Henrik Holmberg Subject: [PATCH] RDMA/bnxt_re: zero shared page before exposing to userspace Date: Sat, 9 May 2026 10:40:11 +0200 Message-ID: <20260509084011.11971-1-pomzm67@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <2026050945-oversight-carefully-93e0@gregkh> References: <2026050945-oversight-carefully-93e0@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Lord Ulf Henrik Holmberg bnxt_re_alloc_ucontext() allocates uctx->shpg via __get_free_page(GFP_KERNEL). The buddy allocator does not zero pages without __GFP_ZERO, so the page contains stale kernel data from whatever object most recently freed it. The page is then mapped into userspace via vm_insert_page() under BNXT_RE_MMAP_SH_PAGE in bnxt_re_mmap(). The driver only ever writes 4 bytes (a u32 AVID) at offset BNXT_RE_AVID_OFFT (0x10) inside bnxt_re_create_ah(); the remaining 4092 bytes of the page are exposed to userspace unsanitised, leaking kernel memory contents. Any user with access to /dev/infiniband/uverbsX on a host with a bnxt_re device (typically rdma group membership) can read this data via a single mmap() at pgoff 0 after IB_USER_VERBS_CMD_GET_CONTEXT. Other shared pages in the same file already use get_zeroed_page() correctly: drivers/infiniband/hw/bnxt_re/ib_verbs.c srq->uctx_srq_page = (void *)get_zeroed_page(GFP_KERNEL); cq->uctx_cq_page = (void *)get_zeroed_page(GFP_KERNEL); uctx->shpg is the only outlier. Bring it in line with the existing convention by switching to get_zeroed_page(). Fixes: 1ac5a4047975 ("RDMA/bnxt_re: Add bnxt_re RoCE driver") Signed-off-by: Lord Ulf Henrik Holmberg --- drivers/infiniband/hw/bnxt_re/ib_verbs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/infiniband/hw/bnxt_re/ib_verbs.c b/drivers/infiniband/hw/bnxt_re/ib_verbs.c index 7ed294516b7e..365ec2767d25 100644 --- a/drivers/infiniband/hw/bnxt_re/ib_verbs.c +++ b/drivers/infiniband/hw/bnxt_re/ib_verbs.c @@ -4638,7 +4638,7 @@ int bnxt_re_alloc_ucontext(struct ib_ucontext *ctx, struct ib_udata *udata) uctx->rdev = rdev; - uctx->shpg = (void *)__get_free_page(GFP_KERNEL); + uctx->shpg = (void *)get_zeroed_page(GFP_KERNEL); if (!uctx->shpg) { rc = -ENOMEM; goto fail; -- 2.47.3