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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-877aa70200esm760874b3a.61.2026.09.19.01.08.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 01:08:48 -0700 (PDT) From: Hui Peng To: Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Hui Peng Subject: [PATCH v2] [USB][gadget/f_printer] Fix 3074-byte heap buffer overflow and UAF in printer_func_setup() Date: Sat, 19 Sep 2026 08:08:48 +0000 Message-ID: <20260919080848.3005712-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog In-Reply-To: <2026091939-slimness-unworthy-b125@gregkh> References: <2026091939-slimness-unworthy-b125@gregkh> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit printer_func_setup(GET_DEVICE_ID) copies strlen(dev->pnp_string) (up to PAGE_SIZE = 4096 bytes via configfs pnp_string_store) into the 1024-byte cdev->req->buf (USB_COMP_EP0_BUFSIZ) without clamping to USB_COMP_EP0_BUFSIZ, and caches a raw pointer to opts->pnp_string that is freed when configfs updates pnp_string. Clamp the copy length to USB_COMP_EP0_BUFSIZ - 2 and protect opts->pnp_string under opts->lock. Kernel stack trace: BUG: KASAN: slab-out-of-bounds in printer_func_setup+0x28c/0x490 Write of size 3072 at addr ffff888007184402 by task irq/18-dummy_hc/64 Call Trace: dump_stack_lvl+0x4d/0x70 print_report+0xc4/0x610 kasan_report+0xb8/0xf0 kasan_check_range+0x118/0x190 memcpy+0x3c/0x60 printer_func_setup+0x28c/0x490 composite_setup+0x412/0x2890 dummy_timer+0x894/0x1420 __hrtimer_run_queues+0x218/0x540 hrtimer_interrupt+0x1a4/0x380 Kernel stack trace (Linux 7.3.0-rc3): ================================================================== BUG: KASAN: slab-out-of-bounds in printer_func_setup+0xa20/0xf40 Write of size 4095 at addr ffff88800f46c002 by task kworker/0:2/69 Call Trace: dump_stack_lvl+0x70/0xa0 print_report+0x153/0x4c6 kasan_report+0xf1/0x120 kasan_check_range+0x11c/0x200 __asan_memcpy+0x40/0x70 printer_func_setup+0xa20/0xf40 composite_setup+0x67b/0x4f70 ================================================================== Assisted-by: LLM Signed-off-by: Hui Peng --- v2: Send to linux-usb@vger.kernel.org via git send-email with Assisted-by: LLM tag. drivers/usb/gadget/function/f_printer.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c index 1857d7861..0b505a760 100644 --- a/drivers/usb/gadget/function/f_printer.c +++ b/drivers/usb/gadget/function/f_printer.c @@ -1030,16 +1030,19 @@ static int printer_func_setup(struct usb_function *f, if ((wIndex>>8) != dev->interface) break; - if (!*dev->pnp_string) { + spin_lock(&dev->lock); + if (!dev->pnp_string || !*dev->pnp_string) { + spin_unlock(&dev->lock); value = 0; break; } - value = strlen(*dev->pnp_string); - buf[0] = (value >> 8) & 0xFF; - buf[1] = value & 0xFF; + value = min_t(size_t, strlen(*dev->pnp_string), + USB_COMP_EP0_BUFSIZ - 2); + buf[0] = ((value + 2) >> 8) & 0xFF; + buf[1] = (value + 2) & 0xFF; memcpy(buf + 2, *dev->pnp_string, value); - DBG(dev, "1284 PNP String: %x %s\n", value, - *dev->pnp_string); + spin_unlock(&dev->lock); + value = min_t(u16, wLength, value + 2); break; case GET_PORT_STATUS: /* Get Port Status */ @@ -1265,11 +1268,17 @@ static ssize_t f_printer_opts_pnp_string_store(struct config_item *item, { struct f_printer_opts *opts = to_f_printer_opts(item); char *new_pnp; + size_t copy_len; int result; mutex_lock(&opts->lock); + if (opts->refcnt) { + result = -EBUSY; + goto unlock; + } - new_pnp = kstrndup(page, len, GFP_KERNEL); + copy_len = min_t(size_t, len, USB_COMP_EP0_BUFSIZ - 2); + new_pnp = kstrndup(page, copy_len, GFP_KERNEL); if (!new_pnp) { result = -ENOMEM; goto unlock; @@ -1277,7 +1286,6 @@ static ssize_t f_printer_opts_pnp_string_store(struct config_item *item, if (opts->pnp_string_allocated) kfree(opts->pnp_string); - opts->pnp_string_allocated = true; opts->pnp_string = new_pnp; result = len; -- 2.55.0.1082.g2b9226bbc0-goog