ext4: check EA value offset when loading
When loading extended attributes, check each entry's value offset to
make sure it doesn't collide with the entries.
Without this check it is easy to crash the kernel by mounting a
malicious FS containing a file with an EA wherein e_value_offs = 0 and
e_value_size > 0 and then deleting the EA, which corrupts the name
list.
(See the f_ea_value_crash test's FS image in e2fsprogs for an example.)
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index da4df70..42823ab 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -190,14 +190,28 @@
}
static int
-ext4_xattr_check_names(struct ext4_xattr_entry *entry, void *end)
+ext4_xattr_check_names(struct ext4_xattr_entry *entry, void *end,
+ void *value_start)
{
- while (!IS_LAST_ENTRY(entry)) {
- struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(entry);
+ struct ext4_xattr_entry *e = entry;
+
+ while (!IS_LAST_ENTRY(e)) {
+ struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(e);
if ((void *)next >= end)
return -EIO;
- entry = next;
+ e = next;
}
+
+ while (!IS_LAST_ENTRY(entry)) {
+ if (entry->e_value_size != 0 &&
+ (value_start + le16_to_cpu(entry->e_value_offs) <
+ (void *)e + sizeof(__u32) ||
+ value_start + le16_to_cpu(entry->e_value_offs) +
+ le32_to_cpu(entry->e_value_size) > end))
+ return -EIO;
+ entry = EXT4_XATTR_NEXT(entry);
+ }
+
return 0;
}
@@ -214,7 +228,8 @@
return -EIO;
if (!ext4_xattr_block_csum_verify(inode, bh->b_blocknr, BHDR(bh)))
return -EIO;
- error = ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size);
+ error = ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size,
+ bh->b_data);
if (!error)
set_buffer_verified(bh);
return error;
@@ -331,7 +346,7 @@
header = IHDR(inode, raw_inode);
entry = IFIRST(header);
end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
- error = ext4_xattr_check_names(entry, end);
+ error = ext4_xattr_check_names(entry, end, entry);
if (error)
goto cleanup;
error = ext4_xattr_find_entry(&entry, name_index, name,
@@ -463,7 +478,7 @@
raw_inode = ext4_raw_inode(&iloc);
header = IHDR(inode, raw_inode);
end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
- error = ext4_xattr_check_names(IFIRST(header), end);
+ error = ext4_xattr_check_names(IFIRST(header), end, IFIRST(header));
if (error)
goto cleanup;
error = ext4_xattr_list_entries(dentry, IFIRST(header),
@@ -980,7 +995,8 @@
is->s.here = is->s.first;
is->s.end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
if (ext4_test_inode_state(inode, EXT4_STATE_XATTR)) {
- error = ext4_xattr_check_names(IFIRST(header), is->s.end);
+ error = ext4_xattr_check_names(IFIRST(header), is->s.end,
+ IFIRST(header));
if (error)
return error;
/* Find the named attribute. */