From 525cac75740542e23c31cd0f248f9b29ae4978e9 Mon Sep 17 00:00:00 2001 From: Daniel Scheller Date: Wed, 9 May 2018 16:08:00 -0400 Subject: [PATCH] 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: daeeb1319e6f ("media: ddbridge: initial support for MCI-based MaxSX8 cards") Reported-by: Colin Ian King Cc: Ralph Metzler Signed-off-by: Daniel Scheller Signed-off-by: Mauro Carvalho Chehab --- drivers/media/pci/ddbridge/ddbridge-mci.c | 21 +++++++++++---------- drivers/media/pci/ddbridge/ddbridge-mci.h | 4 ++++ 2 files changed, 15 insertions(+), 10 deletions(-) diff --git a/drivers/media/pci/ddbridge/ddbridge-mci.c b/drivers/media/pci/ddbridge/ddbridge-mci.c index a85ff3e6b919..8d9592e75ad5 100644 --- a/drivers/media/pci/ddbridge/ddbridge-mci.c +++ b/drivers/media/pci/ddbridge/ddbridge-mci.c @@ -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) { diff --git a/drivers/media/pci/ddbridge/ddbridge-mci.h b/drivers/media/pci/ddbridge/ddbridge-mci.h index c4193c5ee095..453dcb9f8208 100644 --- a/drivers/media/pci/ddbridge/ddbridge-mci.h +++ b/drivers/media/pci/ddbridge/ddbridge-mci.h @@ -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)