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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: daeeb1319e ("media: ddbridge: initial support for MCI-based MaxSX8 cards")

Reported-by: Colin Ian King <colin.king@canonical.com>
Cc: Ralph Metzler <rjkm@metzlerbros.de>
Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
This commit is contained in:
Daniel Scheller 2018-05-09 16:08:00 -04:00 committed by Mauro Carvalho Chehab
parent d7832cd2a3
commit 525cac7574
2 changed files with 15 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
drivers/media/pci/ddbridge/ddbridge-mci.c
View File

@ -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);
state->base->demod_in_use[state->demod] = 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) {

4
drivers/media/pci/ddbridge/ddbridge-mci.h
View File

@ -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)