[PATCH] bna: prevent bad user input in bnad_debugfs_write_regrd()

[Miaoqian Lin <linmq006@gmail.com>]

A malicious user could pass an arbitrarily bad value
to memdup_user_nul(), potentially causing kernel crash.

This follows the same pattern as commit ee76746387f6
("netdevsim: prevent bad user input in nsim_dev_health_break_write()")
and commit 7ef4c19d245f
("smackfs: restrict bytes count in smackfs write functions")

Found via static analysis and code review.

Fixes: d0e6a8064c42 ("bna: use memdup_user to copy userspace buffers")
Cc: stable@vger.kernel.org
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
---
 drivers/net/ethernet/brocade/bna/bnad_debugfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/brocade/bna/bnad_debugfs.c b/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
index 8f0972e6737c..ad33ab1d266d 100644
--- a/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
+++ b/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
@@ -311,6 +311,9 @@ bnad_debugfs_write_regrd(struct file *file, const char __user *buf,
 	unsigned long flags;
 	void *kern_buf;
 
+	if (nbytes == 0 || nbytes > PAGE_SIZE)
+		return -EINVAL;
+
 	/* Copy the user space buf */
 	kern_buf = memdup_user_nul(buf, nbytes);
 	if (IS_ERR(kern_buf))
-- 
2.39.5 (Apple Git-154)