linux-ext4 - [PATCH 2/2] ext4: remove ext4_xattr_check

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Date:   Tue, 14 Mar 2017 21:50:56 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     linux-ext4@...r.kernel.org
Cc:     Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Eric Biggers <ebiggers@...gle.com>
Subject: [PATCH 2/2] ext4: remove ext4_xattr_check_entry()

From: Eric Biggers <ebiggers@...gle.com>

ext4_xattr_check_entry() was redundant with validation of the full xattr
entries list in ext4_xattr_check_entries(), which all callers also did.
ext4_xattr_check_entry() also didn't actually do correct validation;
specifically, it never checked that the value doesn't overlap the xattr
names, nor did it account for padding when checking whether the xattr
value overflows the available space.  So remove it to eliminate any
potential confusion.

Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 fs/ext4/xattr.c | 30 ++++++------------------------
 1 file changed, 6 insertions(+), 24 deletions(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 71bf40933bbb..b4364612a66f 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -249,20 +249,9 @@ __xattr_check_inode(struct inode *inode, struct ext4_xattr_ibody_header *header,
 #define xattr_check_inode(inode, header, end) \
 	__xattr_check_inode((inode), (header), (end), __func__, __LINE__)
 
-static inline int
-ext4_xattr_check_entry(struct ext4_xattr_entry *entry, size_t size)
-{
-	size_t value_size = le32_to_cpu(entry->e_value_size);
-
-	if (entry->e_value_block != 0 || value_size > size ||
-	    le16_to_cpu(entry->e_value_offs) + value_size > size)
-		return -EFSCORRUPTED;
-	return 0;
-}
-
 static int
 ext4_xattr_find_entry(struct ext4_xattr_entry **pentry, int name_index,
-		      const char *name, size_t size, int sorted)
+		      const char *name, int sorted)
 {
 	struct ext4_xattr_entry *entry;
 	size_t name_len;
@@ -282,8 +271,6 @@ ext4_xattr_find_entry(struct ext4_xattr_entry **pentry, int name_index,
 			break;
 	}
 	*pentry = entry;
-	if (!cmp && ext4_xattr_check_entry(entry, size))
-		return -EFSCORRUPTED;
 	return cmp ? -ENODATA : 0;
 }
 
@@ -311,7 +298,6 @@ ext4_xattr_block_get(struct inode *inode, int name_index, const char *name,
 	ea_bdebug(bh, "b_count=%d, refcount=%d",
 		atomic_read(&(bh->b_count)), le32_to_cpu(BHDR(bh)->h_refcount));
 	if (ext4_xattr_check_block(inode, bh)) {
-bad_block:
 		EXT4_ERROR_INODE(inode, "bad block %llu",
 				 EXT4_I(inode)->i_file_acl);
 		error = -EFSCORRUPTED;
@@ -319,9 +305,7 @@ ext4_xattr_block_get(struct inode *inode, int name_index, const char *name,
 	}
 	ext4_xattr_cache_insert(ext4_mb_cache, bh);
 	entry = BFIRST(bh);
-	error = ext4_xattr_find_entry(&entry, name_index, name, bh->b_size, 1);
-	if (error == -EFSCORRUPTED)
-		goto bad_block;
+	error = ext4_xattr_find_entry(&entry, name_index, name, 1);
 	if (error)
 		goto cleanup;
 	size = le32_to_cpu(entry->e_value_size);
@@ -358,13 +342,12 @@ ext4_xattr_ibody_get(struct inode *inode, int name_index, const char *name,
 		return error;
 	raw_inode = ext4_raw_inode(&iloc);
 	header = IHDR(inode, raw_inode);
-	entry = IFIRST(header);
 	end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
 	error = xattr_check_inode(inode, header, end);
 	if (error)
 		goto cleanup;
-	error = ext4_xattr_find_entry(&entry, name_index, name,
-				      end - (void *)entry, 0);
+	entry = IFIRST(header);
+	error = ext4_xattr_find_entry(&entry, name_index, name, 0);
 	if (error)
 		goto cleanup;
 	size = le32_to_cpu(entry->e_value_size);
@@ -799,7 +782,7 @@ ext4_xattr_block_find(struct inode *inode, struct ext4_xattr_info *i,
 		bs->s.end = bs->bh->b_data + bs->bh->b_size;
 		bs->s.here = bs->s.first;
 		error = ext4_xattr_find_entry(&bs->s.here, i->name_index,
-					      i->name, bs->bh->b_size, 1);
+					      i->name, 1);
 		if (error && error != -ENODATA)
 			goto cleanup;
 		bs->s.not_found = error;
@@ -1068,8 +1051,7 @@ int ext4_xattr_ibody_find(struct inode *inode, struct ext4_xattr_info *i,
 			return error;
 		/* Find the named attribute. */
 		error = ext4_xattr_find_entry(&is->s.here, i->name_index,
-					      i->name, is->s.end -
-					      (void *)is->s.base, 0);
+					      i->name, 0);
 		if (error && error != -ENODATA)
 			return error;
 		is->s.not_found = error;
-- 
2.12.0