linux-ext4 - [PATCH v2 2/2] ext2: introduce helper for xattr entry validation

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Date:   Tue, 14 May 2019 06:40:42 +0800
From:   Chengguang Xu <cgxu519@...o.com.cn>
To:     jack@...e.com
Cc:     linux-ext4@...r.kernel.org, Chengguang Xu <cgxu519@...o.com.cn>
Subject: [PATCH v2 2/2] ext2: introduce helper for xattr entry validation

Introduce helper function ext2_xattr_entry_valid()
for xattr entry validation and clean up the entry
check ralated code.

Signed-off-by: Chengguang Xu <cgxu519@...o.com.cn>
---
v1->v2:
- Pass end offset instead of inode to ext2_xattr_entry_valid()
- Change signed-off mail address.

 fs/ext2/xattr.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
index db27260d6a5b..d11c83529514 100644
--- a/fs/ext2/xattr.c
+++ b/fs/ext2/xattr.c
@@ -144,6 +144,20 @@ ext2_xattr_header_valid(struct ext2_xattr_header *header)
 	return true;
 }
 
+static bool
+ext2_xattr_entry_valid(struct ext2_xattr_entry *entry, size_t size,
+		       size_t end_offs)
+{
+	if (entry->e_value_block != 0)
+		return false;
+
+	if (size > end_offs ||
+	    le16_to_cpu(entry->e_value_offs) + size > end_offs)
+		return false;
+
+	return true;
+}
+
 /*
  * ext2_xattr_get()
  *
@@ -217,8 +231,7 @@ ext2_xattr_get(struct inode *inode, int name_index, const char *name,
 	if (entry->e_value_block != 0)
 		goto bad_block;
 	size = le32_to_cpu(entry->e_value_size);
-	if (size > inode->i_sb->s_blocksize ||
-	    le16_to_cpu(entry->e_value_offs) + size > inode->i_sb->s_blocksize)
+	if (!ext2_xattr_entry_valid(entry, size, inode->i_sb->s_blocksize))
 		goto bad_block;
 
 	if (ext2_xattr_cache_insert(ea_block_cache, bh))
@@ -483,8 +496,8 @@ ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 		if (!here->e_value_block && here->e_value_size) {
 			size_t size = le32_to_cpu(here->e_value_size);
 
-			if (le16_to_cpu(here->e_value_offs) + size > 
-			    sb->s_blocksize || size > sb->s_blocksize)
+			if (!ext2_xattr_entry_valid(here, size,
+			    inode->i_sb->s_blocksize))
 				goto bad_block;
 			free += EXT2_XATTR_SIZE(size);
 		}
-- 
2.17.2