Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 525cac75 authored by Daniel Scheller's avatar Daniel Scheller Committed by Mauro Carvalho Chehab
Browse files

media: ddbridge/mci: protect against out-of-bounds array access in stop() 



In stop(), an (unlikely) out-of-bounds write error can occur when setting
the demod_in_use element indexed by state->demod to zero, as state->demod
isn't checked for being in the range of the array size of demod_in_use, and
state->demod maybe carrying the magic 0xff (demod unused) value. Prevent
this by checking state->demod not exceeding the array size before setting
the element value. To make the code a bit easier to read, replace the magic
value and the number of array elements with defines, and use them at a few
more places.

Detected by CoverityScan, CID#1468550 ("Out-of-bounds write")

Thanks to Colin for reporting the problem and providing an initial patch.

Fixes: daeeb131 ("media: ddbridge: initial support for MCI-based MaxSX8 cards")

Reported-by: default avatarColin Ian King <colin.king@canonical.com>
Cc: Ralph Metzler <rjkm@metzlerbros.de>
Signed-off-by: default avatarDaniel Scheller <d.scheller@gmx.net>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+samsung@kernel.org>
parent d7832cd2

drivers/media/pci/ddbridge/ddbridge-mci.c

+11 −10
Original line number Diff line number Diff line
@@ -38,10 +38,10 @@ struct mci_base { 
	struct mutex         mci_lock; /* concurrent MCI access lock */

	int                  count;



	u8                   tuner_use_count[4];

	u8                   assigned_demod[8];

	u32                  used_ldpc_bitrate[8];

	u8                   demod_in_use[8];

	u8                   tuner_use_count[MCI_TUNER_MAX];

	u8                   assigned_demod[MCI_DEMOD_MAX];

	u32                  used_ldpc_bitrate[MCI_DEMOD_MAX];

	u8                   demod_in_use[MCI_DEMOD_MAX];

	u32                  iq_mode;

};
@@ -193,7 +193,7 @@ static int stop(struct dvb_frontend *fe) 
	u32 input = state->tuner;



	memset(&cmd, 0, sizeof(cmd));

	if (state->demod != 0xff) {

	if (state->demod != DEMOD_UNUSED) {

		cmd.command = MCI_CMD_STOP;

		cmd.demod = state->demod;

		mci_cmd(state, &cmd, NULL);
@@ -209,10 +209,11 @@ static int stop(struct dvb_frontend *fe) 
	state->base->tuner_use_count[input]--;

	if (!state->base->tuner_use_count[input])

		mci_set_tuner(fe, input, 0);

	if (state->demod < MCI_DEMOD_MAX)

		state->base->demod_in_use[state->demod] = 0;

	state->base->used_ldpc_bitrate[state->nr] = 0;

	state->demod = 0xff;

	state->base->assigned_demod[state->nr] = 0xff;

	state->demod = DEMOD_UNUSED;

	state->base->assigned_demod[state->nr] = DEMOD_UNUSED;

	state->base->iq_mode = 0;

	mutex_unlock(&state->base->tuner_lock);

	state->started = 0;
@@ -250,7 +251,7 @@ static int start(struct dvb_frontend *fe, u32 flags, u32 modmask, u32 ts_config) 
		stat = -EBUSY;

		goto unlock;

	}

	for (i = 0; i < 8; i++) {

	for (i = 0; i < MCI_DEMOD_MAX; i++) {

		used_ldpc_bitrate += state->base->used_ldpc_bitrate[i];

		if (state->base->demod_in_use[i])

			used_demods++;
@@ -342,7 +343,7 @@ static int start_iq(struct dvb_frontend *fe, u32 ts_config) 
		stat = -EBUSY;

		goto unlock;

	}

	for (i = 0; i < 8; i++)

	for (i = 0; i < MCI_DEMOD_MAX; i++)

		if (state->base->demod_in_use[i])

			used_demods++;

	if (used_demods > 0) {

drivers/media/pci/ddbridge/ddbridge-mci.h

+4 −0
Original line number Diff line number Diff line
@@ -19,6 +19,10 @@ 
#ifndef _DDBRIDGE_MCI_H_

#define _DDBRIDGE_MCI_H_



#define MCI_DEMOD_MAX                       8

#define MCI_TUNER_MAX                       4

#define DEMOD_UNUSED                        (0xFF)



#define MCI_CONTROL                         (0x500)

#define MCI_COMMAND                         (0x600)

#define MCI_RESULT                          (0x680)