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hw/misc/bcm2835_property: Avoid overflow in OTP access properties 

Coverity points out that in our handling of the property
RPI_FWREQ_SET_CUSTOMER_OTP we have a potential overflow.  This
happens because we read start_num and number from the guest as
unsigned 32 bit integers, but then the variable 'n' we use as a loop
counter as we iterate from start_num to start_num + number is only an
"int".  That means that if the guest passes us a very large start_num
we will interpret it as negative.  This will result in an assertion
failure inside bcm2835_otp_set_row(), which checks that we didn't
pass it an invalid row number.

A similar issue applies to all the properties for accessing OTP rows
where we are iterating through with a start and length read from the
guest.

Use uint32_t for the loop counter to avoid this problem. Because in
all cases 'n' is only used as a loop counter, we can do this as
part of the for(), restricting its scope to exactly where we need it.

Resolves: Coverity CID 1549401
Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240723131029.1159908-3-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2024-07-23 14:10:27 +01:00
parent 0892fffc2a
commit 32f1c201ee
1 changed files with 4 additions and 5 deletions
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9
hw/misc/bcm2835_property.c
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@ -30,7 +30,6 @@ static void bcm2835_property_mbox_push(BCM2835PropertyState *s, uint32_t value)
uint32_t tot_len;
size_t resplen;
uint32_t tmp;
int n;
uint32_t start_num, number, otp_row;
/*
@ -337,7 +336,7 @@ static void bcm2835_property_mbox_push(BCM2835PropertyState *s, uint32_t value)
resplen = 8 + 4 * number;
for (n = start_num; n < start_num + number &&
for (uint32_t n = start_num; n < start_num + number &&
n < BCM2835_OTP_CUSTOMER_OTP_LEN; n++) {
otp_row = bcm2835_otp_get_row(s->otp,
BCM2835_OTP_CUSTOMER_OTP + n);
@ -366,7 +365,7 @@ static void bcm2835_property_mbox_push(BCM2835PropertyState *s, uint32_t value)
break;
}
for (n = start_num; n < start_num + number &&
for (uint32_t n = start_num; n < start_num + number &&
n < BCM2835_OTP_CUSTOMER_OTP_LEN; n++) {
otp_row = ldl_le_phys(&s->dma_as,
value + 20 + ((n - start_num) << 2));
@ -383,7 +382,7 @@ static void bcm2835_property_mbox_push(BCM2835PropertyState *s, uint32_t value)
resplen = 8 + 4 * number;
for (n = start_num; n < start_num + number &&
for (uint32_t n = start_num; n < start_num + number &&
n < BCM2835_OTP_PRIVATE_KEY_LEN; n++) {
otp_row = bcm2835_otp_get_row(s->otp,
BCM2835_OTP_PRIVATE_KEY + n);
@ -403,7 +402,7 @@ static void bcm2835_property_mbox_push(BCM2835PropertyState *s, uint32_t value)
break;
}
for (n = start_num; n < start_num + number &&
for (uint32_t n = start_num; n < start_num + number &&
n < BCM2835_OTP_PRIVATE_KEY_LEN; n++) {
otp_row = ldl_le_phys(&s->dma_as,
value + 20 + ((n - start_num) << 2));