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([2402:f000:4:1006:809:0:a77:18ea]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7ff7a843a18sm45972843b3a.14.2026.01.04.08.54.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 04 Jan 2026 08:54:17 -0800 (PST) From: Tuo Li To: philipp.reisner@linbit.com, lars.ellenberg@linbit.com, christoph.boehmwalder@linbit.com, axboe@kernel.dk Cc: drbd-dev@lists.linbit.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Tuo Li Subject: [PATCH] drbd: fix a null-pointer dereference when the request event in drbd_request_endio() is READ_COMPLETED_WITH_ERROR Date: Mon, 5 Jan 2026 00:53:55 +0800 Message-ID: <20260104165355.151864-1-islituo@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" In drbd_request_endio(), the request event what can be set to READ_COMPLETED_WITH_ERROR. In this case, __req_mod() is invoked with a NULL peer_device: __req_mod(req, what, NULL, &m); When handling READ_COMPLETED_WITH_ERROR, __req_mod() unconditionally calls drbd_set_out_of_sync(): case READ_COMPLETED_WITH_ERROR: drbd_set_out_of_sync(peer_device, req->i.sector, req->i.size); The drbd_set_out_of_sync() macro expands to __drbd_change_sync(): #define drbd_set_out_of_sync(peer_device, sector, size) \ __drbd_change_sync(peer_device, sector, size, SET_OUT_OF_SYNC) However, __drbd_change_sync() assumes a valid peer_device and immediately dereferences it: struct drbd_device *device =3D peer_device->device; If peer_device is NULL, this results in a NULL-pointer dereference. Fix this by adding a NULL check in __req_mod() before calling drbd_set_out_of_sync(). Signed-off-by: Tuo Li --- drivers/block/drbd/drbd_req.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c index d15826f6ee81..aa3da2733f14 100644 --- a/drivers/block/drbd/drbd_req.c +++ b/drivers/block/drbd/drbd_req.c @@ -621,7 +621,8 @@ int __req_mod(struct drbd_request *req, enum drbd_req_e= vent what, break; =20 case READ_COMPLETED_WITH_ERROR: - drbd_set_out_of_sync(peer_device, req->i.sector, req->i.size); + if (peer_device) + drbd_set_out_of_sync(peer_device, req->i.sector, req->i.size); drbd_report_io_error(device, req); __drbd_chk_io_error(device, DRBD_READ_ERROR); fallthrough; --=20 2.43.0