From cf24991619be317e2769310b4a367bf4a04b82bc Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Mon, 20 Apr 2026 18:11:04 +0200 Subject: [PATCH] usb: usblp: fix uninitialized heap leak via LPGETSTATUS ioctl commit b38e53cbfb9d84732e5984fbd73e128d592415c5 upstream. Just like in a previous problem in this driver, usblp_ctrl_msg() will collapse the usb_control_msg() return value to 0/-errno, discarding the actual number of bytes transferred. Ideally that short command should be detected and error out, but many printers are known to send "incorrect" responses back so we can't just do that. statusbuf is kmalloc(8) at probe time and never filled before the first LPGETSTATUS ioctl. usblp_read_status() requests 1 byte. If a malicious printer responds with zero bytes, *statusbuf is one byte of stale kmalloc heap, sign-extended into the local int status, which the LPGETSTATUS path then copy_to_user()s directly to the ioctl caller. Fix this all by just zapping out the memory buffer when allocated at probe time. If a later call does a short read, the data will be identical to what the device sent it the last time, so there is no "leak" of information happening. Cc: Pete Zaitcev Assisted-by: gkh_clanker_t1000 Cc: stable Link: https://patch.msgid.link/2026042011-shredder-savage-48c6@gregkh Signed-off-by: Greg Kroah-Hartman --- drivers/usb/class/usblp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c index 7bc3f7526d3d..b76055658488 100644 --- a/drivers/usb/class/usblp.c +++ b/drivers/usb/class/usblp.c @@ -1166,7 +1166,7 @@ static int usblp_probe(struct usb_interface *intf, } /* Allocate buffer for printer status */ - usblp->statusbuf = kmalloc(STATUS_BUF_SIZE, GFP_KERNEL); + usblp->statusbuf = kzalloc(STATUS_BUF_SIZE, GFP_KERNEL); if (!usblp->statusbuf) { retval = -ENOMEM; goto abort;