fs/ntfs3: fix slab-out-of-bounds write in ni_create_attr_list()

ni_create_attr_list() allocates a fixed buffer of al_aligned(record_size)
(== record_size) bytes and then walks every attribute of the primary MFT
record, writing one ATTR_LIST_ENTRY per attribute and advancing the cursor
by le_size(name_len), with no check against the end of the buffer; the
total size is only computed after the loop.

A minimum-size resident attribute occupies SIZEOF_RESIDENT (0x18 = 24)
bytes on disk, but an unnamed attribute expands to le_size(0) (0x20 = 32)
bytes in the list.  Because the number of attributes in a record is not
bounded (mi_enum_attr() accepts arbitrarily many equal-type, nameless
minimum-size attributes), a crafted record packed with such attributes
produces a list larger than record_size and overflows the heap buffer.

This is reachable from a crafted, loop-mounted NTFS image: opening the file
and adding an attribute (e.g. via setxattr) drives ntfs_set_ea() ->
ni_insert_resident() -> ni_insert_attr() -> ni_ins_attr_ext() ->
ni_create_attr_list().

  BUG: KASAN: slab-out-of-bounds in ni_create_attr_list+0xc48/0x1058
  Write of size 4 at addr ffff000008984c00 by task setfattr/345
   ni_create_attr_list+0xc48/0x1058
   ni_ins_attr_ext+0x510/0x7c0
   ni_insert_attr+0x3f8/0x70c
   ni_insert_resident+0xc8/0x3b0
   ntfs_set_ea+0x66c/0xd28
   ntfs_setxattr+0x4d8/0x5b0
   __arm64_sys_setxattr+0xa4/0x124
  Allocated by task 345:
   ni_create_attr_list+0x188/0x1058
  The buggy address belongs to the cache kmalloc-1k of size 1024
  (the write lands at object+1024).

Size the buffer from the actual attributes instead of assuming a single
record_size is always enough.

Fixes: 4342306f0f0d ("fs/ntfs3: Add file operations and implementation")
Reported-by: HE WEI（ギカク） <skyexpoc@gmail.com>
Signed-off-by: HE WEI（ギカク） <skyexpoc@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

0 files changed, 0 insertions, 0 deletions