fs/ntfs3: validate ef->size covers the record's name and value

When an EA record has a non-zero ef->size, ntfs_read_ea() only checks
that the record fits in the remaining buffer (ea_size > bytes), not that
ef->size is large enough to hold the record's own name_len + 1 + elength.

A crafted image can pass validation with, e.g., ef->size = 24 but
elength = 0xffff. ntfs_get_ea() then trusts elength and copies it out of
the undersized record, reading past the kmalloc(info->size) allocation
and leaking heap memory to userspace via getxattr():

 BUG: KASAN: slab-out-of-bounds in ntfs_get_ea (fs/ntfs3/xattr.c:302)
 Read of size 65535 at addr ffff888100794550 by task exploit
  __asan_memcpy (mm/kasan/shadow.c:105)
  ntfs_get_ea (fs/ntfs3/xattr.c:302)
  ntfs_getxattr (fs/ntfs3/xattr.c:848)
  __vfs_getxattr (fs/xattr.c:441)
  vfs_getxattr (fs/xattr.c:474)
  do_getxattr (fs/xattr.c:800)
  path_getxattrat (fs/xattr.c:868)
  do_syscall_64 (arch/x86/entry/syscall_64.c:94)

 The buggy address is located 80 bytes inside of
  allocated 84-byte region in cache kmalloc-96

Compute the size the record needs and require ef->size to cover it.

Fixes: 0e8235d28f3a ("fs/ntfs3: Check fields while reading")
Reported-by: Xiang Mei <xmei5@asu.edu>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

0 files changed, 0 insertions, 0 deletions