In the Linux kernel, the following vulnerability has been resolved: mmc: davinci: avoid NULL deref of host->data in IRQ handler mmc_davinc

In the Linux kernel, the following vulnerability has been resolved:

mmc: davinci: avoid NULL deref of host->data in IRQ handler

mmc_davinci_irq() returns early only when both host->cmd and
host->data are NULL:

if (host->cmd == NULL && host->data == NULL) {
...
return IRQ_NONE;
}

So we may legitimately reach the rest of the handler with
host->data == NULL (and therefore data == NULL). The DATDNE branch
already guards against this with an explicit "if (data != NULL)"
check, but the subsequent TOUTRD ("read data timeout") and
CRCWR/CRCRD ("data CRC error") branches dereference data
unconditionally:

if (qstatus & MMCST0_TOUTRD) {
data->error = -ETIMEDOUT; <-- NULL deref
...
davinci_abort_data(host, data);
}

if (qstatus & (MMCST0_CRCWR | MMCST0_CRCRD)) {
data->error = -EILSEQ; <-- NULL deref
...
}

If either bit is set in qstatus while host->data is NULL, the kernel
will crash inside the IRQ handler. smatch flags this:

drivers/mmc/host/davinci_mmc.c:933 mmc_davinci_irq() error: we
previously assumed 'data' could be null (see line 914)

Gate both branches on a non-NULL data, matching the existing pattern
used by the DATDNE branch.

No functional change for callers where data is non-NULL, which is
the only case in which these branches did meaningful work before
this change.