snd_korg1212_create() makes the following steps during initialization
of the card:
1) registers an interrupt handler (lines 2230-2232)
2) allocates and initializes korg1212->sharedBufferPtr (lines 2280-2287)
3) reboots the card via snd_korg1212_Send1212Command() (line 2358)
2145 static int snd_korg1212_create(struct snd_card *card, struct
pci_dev *pci, struct snd_korg1212 **rchip)
2147 {
...
2230 err = request_irq(pci->irq, snd_korg1212_interrupt,
2231 IRQF_SHARED,
2232 KBUILD_MODNAME, korg1212);
...
2280 if (snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV, &pci->dev,
2281 sizeof(struct KorgSharedBuffer), &korg1212->dma_shared) < 0){
2282 snd_printk(KERN_ERR "korg1212: can not
allocate shared buffer memory (%zdbytes)\n",
sizeof(struct KorgSharedBuffer));
2283 snd_korg1212_free(korg1212);
2284 return -ENOMEM;
2285 }
2286 korg1212->sharedBufferPtr =
(struct KorgSharedBuffer*)korg1212->dma_shared.area;
2287 korg1212->sharedBufferPhy = korg1212->dma_shared.addr;
...
2358 rc = snd_korg1212_Send1212Command(korg1212,
K1212_DB_RebootCard, 0, 0, 0, 0);
...
2412 }
But if interrupt happens when snd_korg1212_create() is still within
lines 2233-2286,
snd_korg1212_interrupt() may dereference korg1212->sharedBufferPtr before
it was initialized without any checks (line 1149):
1098 static irqreturn_t snd_korg1212_interrupt(int irq, void *dev_id)
1099 {
...
1116 switch (doorbellValue) {
...
1145 case K1212_DB_CARDSTOPPED:
1146 K1212_DEBUG_PRINTK_VERBOSE("K1212_DEBUG: IRQ
CSTP count - %ld, %x, [%s].\n",
1147 korg1212->irqcount, doorbellValue,
1148 stateName[korg1212->cardState]);
1149 korg1212->sharedBufferPtr->cardCommand = 0;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1150 break;
...
1185 }
Should we be sure that such interrupt cannot happen or
should we move the registration of the interrupt handler after
korg1212->sharedBufferPtr is initialized?
Found by Linux Driver Verification project (linuxtesting.org).
