linux-kernel - [PATCH] ecryptfs: keystore: Fix a buffer overrun in write_tag_66

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Date:   Fri, 30 Jun 2023 17:11:55 +0800
From:   Yiyuan Guo <yguoaz@...il.com>
To:     code@...icks.com
Cc:     viro@...iv.linux.org.uk, brauner@...nel.org,
        ecryptfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        yguoaz@...il.com
Subject: [PATCH] ecryptfs: keystore: Fix a buffer overrun in write_tag_66_packet()

The encrypted key of a TAG 66 Packet includes 1 byte cipher code and 2
byte checksum, but the allocation size `data_len` ignores the extra 3
bytes. Fix the allocation size to avoid buffer overrun.

Signed-off-by: Yiyuan Guo <yguoaz@...il.com>
---
 fs/ecryptfs/keystore.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index 2452d6fd7062..5cab0b800a03 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -302,7 +302,7 @@ write_tag_66_packet(char *signature, u8 cipher_code,
 	 *         | File Encryption Key Size | 1 or 2 bytes |
 	 *         | File Encryption Key      | arbitrary    |
 	 */
-	data_len = (5 + ECRYPTFS_SIG_SIZE_HEX + crypt_stat->key_size);
+	data_len = (5 + ECRYPTFS_SIG_SIZE_HEX + crypt_stat->key_size + 3);
 	*packet = kmalloc(data_len, GFP_KERNEL);
 	message = *packet;
 	if (!message) {
-- 
2.25.1