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.

Signed-off-by: Stepan Ionichev <sozdayvek@gmail.com>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/davinci_mmc.c b/drivers/mmc/host/davinci_mmc.c
index 42b0118a45a8ec8ec9bfad1ff20556b5e24252ad..42ad87aa48f59059a8f220840fe57e9c914cebb1 100644 (file)
--- a/drivers/mmc/host/davinci_mmc.c
+++ b/drivers/mmc/host/davinci_mmc.c
@@ -928,7 +928,7 @@ static irqreturn_t mmc_davinci_irq(int irq, void *dev_id)
                }
        }
 
-       if (qstatus & MMCST0_TOUTRD) {
+       if (data && (qstatus & MMCST0_TOUTRD)) {
                /* Read data timeout */
                data->error = -ETIMEDOUT;
                end_transfer = 1;
@@ -940,7 +940,7 @@ static irqreturn_t mmc_davinci_irq(int irq, void *dev_id)
                davinci_abort_data(host, data);
        }
 
-       if (qstatus & (MMCST0_CRCWR | MMCST0_CRCRD)) {
+       if (data && (qstatus & (MMCST0_CRCWR | MMCST0_CRCRD))) {
                /* Data CRC error */
                data->error = -EILSEQ;
                end_transfer = 1;