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emdtv(4): If register read fails, read as all zero.
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Avoids undefined behaviour if device is yanked or broken.

Reported-by: syzbot+18ce1e017b9f802ed287@syzkaller.appspotmail.com
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riastradh authored and riastradh committed Mar 12, 2022
1 parent 46605d0 commit 6dc364f
Showing 1 changed file with 5 additions and 3 deletions.
8 changes: 5 additions & 3 deletions sys/dev/usb/emdtv.c
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@@ -1,4 +1,4 @@
/* $NetBSD: emdtv.c,v 1.15 2020/03/14 02:35:33 christos Exp $ */
/* $NetBSD: emdtv.c,v 1.16 2022/03/12 18:31:39 riastradh Exp $ */

/*-
* Copyright (c) 2008, 2011 Jared D. McNeill <jmcneill@invisible.ca>
Expand Down Expand Up @@ -27,7 +27,7 @@
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: emdtv.c,v 1.15 2020/03/14 02:35:33 christos Exp $");
__KERNEL_RCSID(0, "$NetBSD: emdtv.c,v 1.16 2022/03/12 18:31:39 riastradh Exp $");

#include <sys/param.h>
#include <sys/systm.h>
Expand Down Expand Up @@ -326,9 +326,11 @@ emdtv_read_multi_1(struct emdtv_softc *sc, uint8_t req, uint16_t index,
status = usbd_do_request(sc->sc_udev, &request, datap);
KERNEL_UNLOCK_ONE(curlwp);

if (status != USBD_NORMAL_COMPLETION)
if (status != USBD_NORMAL_COMPLETION) {
aprint_error_dev(sc->sc_dev, "couldn't read %x/%x: %s\n",
req, index, usbd_errstr(status));
memset(datap, 0, count);
}

if (emdtv_debug_regs) {
int i;
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