diff options
| author | Hao Wu <wuhaotsh@google.com> | 2021-01-26 17:11:42 -0800 |
|---|---|---|
| committer | Peter Maydell <peter.maydell@linaro.org> | 2021-01-29 10:47:28 +0000 |
| commit | 1e5ce6e10a1deaec6044ba8ad75431e0424dbce9 (patch) | |
| tree | 6f2110eeb591c05111c4c95886f6d185956b99c0 /hw | |
| parent | daa726d92604b72650d86ada01935e03a909d4dd (diff) | |
hw/misc: Fix arith overflow in NPCM7XX PWM module
Fix potential overflow problem when calculating pwm_duty.
1. Ensure p->cmr and p->cnr to be from [0,65535], according to the
hardware specification.
2. Changed duty to uint32_t. However, since MAX_DUTY * (p->cmr+1)
can excceed UINT32_MAX, we convert them to uint64_t in computation
and converted them back to uint32_t.
(duty is guaranteed to be <= MAX_DUTY so it won't overflow.)
Fixes: CID 1442342
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Doug Evans <dje@google.com>
Signed-off-by: Hao Wu <wuhaotsh@google.com>
Message-id: 20210127011142.2122790-1-wuhaotsh@google.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Diffstat (limited to 'hw')
| -rw-r--r-- | hw/misc/npcm7xx_pwm.c | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/hw/misc/npcm7xx_pwm.c b/hw/misc/npcm7xx_pwm.c index e99e3cc7ef..dabcb6c0f9 100644 --- a/hw/misc/npcm7xx_pwm.c +++ b/hw/misc/npcm7xx_pwm.c @@ -58,6 +58,9 @@ REG32(NPCM7XX_PWM_PWDR3, 0x50); #define NPCM7XX_CH_INV BIT(2) #define NPCM7XX_CH_MOD BIT(3) +#define NPCM7XX_MAX_CMR 65535 +#define NPCM7XX_MAX_CNR 65535 + /* Offset of each PWM channel's prescaler in the PPR register. */ static const int npcm7xx_ppr_base[] = { 0, 0, 8, 8 }; /* Offset of each PWM channel's clock selector in the CSR register. */ @@ -96,7 +99,7 @@ static uint32_t npcm7xx_pwm_calculate_freq(NPCM7xxPWM *p) static uint32_t npcm7xx_pwm_calculate_duty(NPCM7xxPWM *p) { - uint64_t duty; + uint32_t duty; if (p->running) { if (p->cnr == 0) { @@ -104,7 +107,7 @@ static uint32_t npcm7xx_pwm_calculate_duty(NPCM7xxPWM *p) } else if (p->cmr >= p->cnr) { duty = NPCM7XX_PWM_MAX_DUTY; } else { - duty = NPCM7XX_PWM_MAX_DUTY * (p->cmr + 1) / (p->cnr + 1); + duty = (uint64_t)NPCM7XX_PWM_MAX_DUTY * (p->cmr + 1) / (p->cnr + 1); } } else { duty = 0; @@ -357,7 +360,13 @@ static void npcm7xx_pwm_write(void *opaque, hwaddr offset, case A_NPCM7XX_PWM_CNR2: case A_NPCM7XX_PWM_CNR3: p = &s->pwm[npcm7xx_cnr_index(offset)]; - p->cnr = value; + if (value > NPCM7XX_MAX_CNR) { + qemu_log_mask(LOG_GUEST_ERROR, + "%s: invalid cnr value: %u", __func__, value); + p->cnr = NPCM7XX_MAX_CNR; + } else { + p->cnr = value; + } npcm7xx_pwm_update_output(p); break; @@ -366,7 +375,13 @@ static void npcm7xx_pwm_write(void *opaque, hwaddr offset, case A_NPCM7XX_PWM_CMR2: case A_NPCM7XX_PWM_CMR3: p = &s->pwm[npcm7xx_cmr_index(offset)]; - p->cmr = value; + if (value > NPCM7XX_MAX_CMR) { + qemu_log_mask(LOG_GUEST_ERROR, + "%s: invalid cmr value: %u", __func__, value); + p->cmr = NPCM7XX_MAX_CMR; + } else { + p->cmr = value; + } npcm7xx_pwm_update_output(p); break; |