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Date:   Wed,  9 Oct 2019 11:20:19 +0800
Message-Id: <20191009032019.6954-1-huangrandall@google.com>
Mime-Version: 1.0
Subject: [PATCH] f2fs: fix to avoid memory leakage in f2fs_listxattr
From:   Randall Huang <huangrandall@google.com>
To:     jaegeuk@kernel.org, yuchao0@huawei.com,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Cc:     huangrandall@google.com
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In f2fs_listxattr, there is no boundary check before
memcpy e_name to buffer.
If the e_name_len is corrupted,
unexpected memory contents may be returned to the buffer.

Signed-off-by: Randall Huang <huangrandall@google.com>
---
 fs/f2fs/xattr.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index b32c45621679..acc3663970cd 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -538,8 +538,9 @@ int f2fs_getxattr(struct inode *inode, int index, const char *name,
 ssize_t f2fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 {
 	struct inode *inode = d_inode(dentry);
+	nid_t xnid = F2FS_I(inode)->i_xattr_nid;
 	struct f2fs_xattr_entry *entry;
-	void *base_addr;
+	void *base_addr, *last_base_addr;
 	int error = 0;
 	size_t rest = buffer_size;
 
@@ -549,6 +550,8 @@ ssize_t f2fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 	if (error)
 		return error;
 
+	last_base_addr = (void *)base_addr + XATTR_SIZE(xnid, inode);
+
 	list_for_each_xattr(entry, base_addr) {
 		const struct xattr_handler *handler =
 			f2fs_xattr_handler(entry->e_name_index);
@@ -559,6 +562,15 @@ ssize_t f2fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 		if (!handler || (handler->list && !handler->list(dentry)))
 			continue;
 
+		if ((void *)(entry) + sizeof(__u32) > last_base_addr ||
+			(void *)XATTR_NEXT_ENTRY(entry) > last_base_addr) {
+			f2fs_err(F2FS_I_SB(inode), "inode (%lu) has corrupted xattr",
+						inode->i_ino);
+			set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK);
+			error = -EFSCORRUPTED;
+			goto cleanup;
+		}
+
 		prefix = xattr_prefix(handler);
 		prefix_len = strlen(prefix);
 		size = prefix_len + entry->e_name_len + 1;
-- 
2.23.0.581.g78d2f28ef7-goog