[PATCH 4.4 48/54] regmap: debugfs: check count when read regmap file

Greg Kroah-Hartman
2020-07-30T08:12:47Z

From: Peng Fan <peng.fan@nxp.com>

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@nxp.com>
Link: https://lore.kernel.org/r/1584064687-12964-1-git-send-email-peng.fan@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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
@@ -194,6 +194,9 @@ 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;
@@ -342,6 +345,9 @@ 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;