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Subject[PATCH] mmc: davinci: avoid NULL deref of host->data in IRQ handler
Date
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>
---
drivers/mmc/host/davinci_mmc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/davinci_mmc.c b/drivers/mmc/host/davinci_mmc.c
index 42b0118a4..42ad87aa4 100644
--- 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;
--
2.43.0

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