[PATCH 5.4 17/19] regmap: debugfs: check count when read regmap file

[Greg Kroah-Hartman]

From: Peng Fan <peng.fan@xxxxxxx>

commit 74edd08a4fbf51d65fd8f4c7d8289cd0f392bd91 upstream.

When executing the following command, we met kernel dump.
dmesg -c > /dev/null; cd /sys;
for i in `ls /sys/kernel/debug/regmap/* -d`; do
	echo "Checking regmap in $i";
	cat $i/registers;
done && grep -ri "0x02d0" *;

It is because the count value is too big, and kmalloc fails. So add an
upper bound check to allow max size `PAGE_SIZE << (MAX_ORDER - 1)`.

Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
Link: https://lore.kernel.org/r/1584064687-12964-1-git-send-email-peng.fan@xxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/base/regmap/regmap-debugfs.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -227,6 +227,9 @@ static ssize_t regmap_read_debugfs(struc
 	if (*ppos < 0 || !count)
 		return -EINVAL;
 
+	if (count > (PAGE_SIZE << (MAX_ORDER - 1)))
+		count = PAGE_SIZE << (MAX_ORDER - 1);
+
 	buf = kmalloc(count, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
@@ -371,6 +374,9 @@ static ssize_t regmap_reg_ranges_read_fi
 	if (*ppos < 0 || !count)
 		return -EINVAL;
 
+	if (count > (PAGE_SIZE << (MAX_ORDER - 1)))
+		count = PAGE_SIZE << (MAX_ORDER - 1);
+
 	buf = kmalloc(count, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;