[PATCH] spi: spi-zynq-qspi: Fix a NULL pointer dereference in zynq_qspi_exec_mem_op()

[PATCH] spi: spi-zynq-qspi: Fix a NULL pointer dereference in zynq_qspi_exec_mem_op()

[Zhou Qingyang]

In zynq_qspi_exec_mem_op(), kzalloc() is directly used in memset(),
which could lead to a NULL pointer dereference on failure of
kzalloc().

Fix this bug by adding a check of tmpbuf.

This bug was found by a static analyzer. The analysis employs
differential checking to identify inconsistent security operations
(e.g., checks or kfrees) between two code paths and confirms that the
inconsistent operations are not recovered in the current function or
the callers, so they constitute bugs.

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

Builds with CONFIG_SPI_ZYNQ_QSPI=m show no new warnings,
and our static analyzer no longer warns about this code.

Fixes: 67dca5e580f1 ("spi: spi-mem: Add support for Zynq QSPI controller")
Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
---
 drivers/spi/spi-zynq-qspi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/spi/spi-zynq-qspi.c b/drivers/spi/spi-zynq-qspi.c
index cfa222c9bd5e..78f31b61a2aa 100644
--- a/drivers/spi/spi-zynq-qspi.c
+++ b/drivers/spi/spi-zynq-qspi.c
@@ -570,6 +570,9 @@ static int zynq_qspi_exec_mem_op(struct spi_mem *mem,
 
 	if (op->dummy.nbytes) {
 		tmpbuf = kzalloc(op->dummy.nbytes, GFP_KERNEL);
+		if (!tmpbuf)
+			return -ENOMEM;
+
 		memset(tmpbuf, 0xff, op->dummy.nbytes);
 		reinit_completion(&xqspi->data_completion);
 		xqspi->txbuf = tmpbuf;
-- 
2.25.1

Re: [PATCH] spi: spi-zynq-qspi: Fix a NULL pointer dereference in zynq_qspi_exec_mem_op()

[Mark Brown]

On Wed, 1 Dec 2021 01:22:53 +0800, Zhou Qingyang wrote:
> In zynq_qspi_exec_mem_op(), kzalloc() is directly used in memset(),
> which could lead to a NULL pointer dereference on failure of
> kzalloc().
> 
> Fix this bug by adding a check of tmpbuf.
> 
> This bug was found by a static analyzer. The analysis employs
> differential checking to identify inconsistent security operations
> (e.g., checks or kfrees) between two code paths and confirms that the
> inconsistent operations are not recovered in the current function or
> the callers, so they constitute bugs.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-linus

Thanks!

[1/1] spi: spi-zynq-qspi: Fix a NULL pointer dereference in zynq_qspi_exec_mem_op()
      commit: ab3824427b848da10e9fe2727f035bbeecae6ff4

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark