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hw/misc/bcm2835_property: Fix handling of FRAMEBUFFER_SET_PALETTE 

The documentation of the "Set palette" mailbox property at
https://github.com/raspberrypi/firmware/wiki/Mailbox-property-interface#set-palette
says it has the form:

    Length: 24..1032
    Value:
        u32: offset: first palette index to set (0-255)
        u32: length: number of palette entries to set (1-256)
        u32...: RGBA palette values (offset to offset+length-1)

We get this wrong in a couple of ways:
 * we aren't checking the offset and length are in range, so the guest
   can make us spin for a long time by providing a large length
 * the bounds check on our loop is wrong: we should iterate through
   'length' palette entries, not 'length - offset' entries

Fix the loop to implement the bounds checks and get the loop
condition right. In the process, make the variables local to
this switch case, rather than function-global, so it's clearer
what type they are when reading the code.

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240723131029.1159908-2-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2024-07-23 14:10:26 +01:00
parent 05b8d72491
commit 0892fffc2a
1 changed files with 16 additions and 11 deletions
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27
hw/misc/bcm2835_property.c
View File

@ -31,7 +31,6 @@ static void bcm2835_property_mbox_push(BCM2835PropertyState *s, uint32_t value)
size_t resplen;
uint32_t tmp;
int n;
uint32_t offset, length, color;
uint32_t start_num, number, otp_row;
/*
@ -274,19 +273,25 @@ static void bcm2835_property_mbox_push(BCM2835PropertyState *s, uint32_t value)
resplen = 16;
break;
case RPI_FWREQ_FRAMEBUFFER_SET_PALETTE:
offset = ldl_le_phys(&s->dma_as, value + 12);
length = ldl_le_phys(&s->dma_as, value + 16);
n = 0;
while (n < length - offset) {
color = ldl_le_phys(&s->dma_as, value + 20 + (n << 2));
stl_le_phys(&s->dma_as,
s->fbdev->vcram_base + ((offset + n) << 2), color);
n++;
{
uint32_t offset = ldl_le_phys(&s->dma_as, value + 12);
uint32_t length = ldl_le_phys(&s->dma_as, value + 16);
int resp;
if (offset > 255 || length < 1 || length > 256) {
resp = 1; /* invalid request */
} else {
for (uint32_t e = 0; e < length; e++) {
uint32_t color = ldl_le_phys(&s->dma_as, value + 20 + (e << 2));
stl_le_phys(&s->dma_as,
s->fbdev->vcram_base + ((offset + e) << 2), color);
}
resp = 0;
}
stl_le_phys(&s->dma_as, value + 12, 0);
stl_le_phys(&s->dma_as, value + 12, resp);
resplen = 4;
break;
}
case RPI_FWREQ_FRAMEBUFFER_GET_NUM_DISPLAYS:
stl_le_phys(&s->dma_as, value + 12, 1);
resplen = 4;