From ab3824427b848da10e9fe2727f035bbeecae6ff4 Mon Sep 17 00:00:00 2001
From: Zhou Qingyang <zhou1615@umn.edu>
Date: Wed, 1 Dec 2021 01:22:53 +0800
Subject: [PATCH] spi: spi-zynq-qspi: Fix a NULL pointer dereference in zynq_qspi_exec_mem_op()
Git-commit: ab3824427b848da10e9fe2727f035bbeecae6ff4
Patch-mainline: v5.17-rc6
References: git-fixes

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>
Link: https://lore.kernel.org/r/20211130172253.203700-1-zhou1615@umn.edu
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 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;
-- 
2.31.1