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From:   gregory.greenman@intel.com
To:     johannes@sipsolutions.net
Cc:     linux-wireless@vger.kernel.org, Hyunwoo Kim <imv4bel@gmail.com>,
        Gregory Greenman <gregory.greenman@intel.com>
Subject: [PATCH 08/15] wifi: iwlwifi: pcie: Fix integer overflow in iwl_write_to_user_buf
Date:   Fri, 14 Apr 2023 13:11:59 +0300
Message-Id: <20230414130637.2d80ace81532.Iecfba549e0e0be21bbb0324675392e42e75bd5ad@changeid>
In-Reply-To: <20230414101206.1170180-1-gregory.greenman@intel.com>
References: <20230414101206.1170180-1-gregory.greenman@intel.com>
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From: Hyunwoo Kim <imv4bel@gmail.com>

An integer overflow occurs in the iwl_write_to_user_buf() function,
which is called by the iwl_dbgfs_monitor_data_read() function.

static bool iwl_write_to_user_buf(char __user *user_buf, ssize_t count,
				  void *buf, ssize_t *size,
				  ssize_t *bytes_copied)
{
	int buf_size_left = count - *bytes_copied;

	buf_size_left = buf_size_left - (buf_size_left % sizeof(u32));
	if (*size > buf_size_left)
		*size = buf_size_left;

If the user passes a SIZE_MAX value to the "ssize_t count" parameter,
the ssize_t count parameter is assigned to "int buf_size_left".
Then compare "*size" with "buf_size_left" . Here, "buf_size_left" is a
negative number, so "*size" is assigned "buf_size_left" and goes into
the third argument of the copy_to_user function, causing a heap overflow.

This is not a security vulnerability because iwl_dbgfs_monitor_data_read()
is a debugfs operation with 0400 privileges.

Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
---
 drivers/net/wireless/intel/iwlwifi/pcie/trans.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
index 40283fe622da..1b32a4035d88 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
@@ -2860,7 +2860,7 @@ static bool iwl_write_to_user_buf(char __user *user_buf, ssize_t count,
 				  void *buf, ssize_t *size,
 				  ssize_t *bytes_copied)
 {
-	int buf_size_left = count - *bytes_copied;
+	ssize_t buf_size_left = count - *bytes_copied;
 
 	buf_size_left = buf_size_left - (buf_size_left % sizeof(u32));
 	if (*size > buf_size_left)
-- 
2.38.1