mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-08-24 09:50:04 +00:00
Code Issues Releases Wiki Activity

keys: Fix description size

Browse source 
The maximum key description size is 4095.  Commit f771fde820 ("keys:
Simplify key description management") inadvertantly reduced that to 255
and made sizes between 256 and 4095 work weirdly, and any size whereby
size & 255 == 0 would cause an assertion in __key_link_begin() at the
following line:

	BUG_ON(index_key->desc_len == 0);

This can be fixed by simply increasing the size of desc_len in struct
keyring_index_key to a u16.

Note the argument length test in keyutils only checked empty
descriptions and descriptions with a size around the limit (ie.  4095)
and not for all the values in between, so it missed this.  This has been
addressed and

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git/commit/?id=066bf56807c26cd3045a25f355b34c1d8a20a5aa

now exhaustively tests all possible lengths of type, description and
payload and then some.

The assertion failure looks something like:

 kernel BUG at security/keys/keyring.c:1245!
 ...
 RIP: 0010:__key_link_begin+0x88/0xa0
 ...
 Call Trace:
  key_create_or_update+0x211/0x4b0
  __x64_sys_add_key+0x101/0x200
  do_syscall_64+0x5b/0x1e0
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

It can be triggered by:

	keyctl add user "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" a @s

Fixes: f771fde820 ("keys: Simplify key description management")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Howells 2019-08-19 16:02:01 +01:00 committed by Linus Torvalds
parent d1abaeb3be
commit 555df336c7
1 changed files with 4 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
include/linux/key.h
View file

@ -94,11 +94,11 @@ struct keyring_index_key {
union {
struct {
#ifdef __LITTLE_ENDIAN /* Put desc_len at the LSB of x */
u8 desc_len;
char desc[sizeof(long) - 1]; /* First few chars of description */
u16 desc_len;
char desc[sizeof(long) - 2]; /* First few chars of description */
#else
char desc[sizeof(long) - 1]; /* First few chars of description */
u8 desc_len;
char desc[sizeof(long) - 2]; /* First few chars of description */
u16 desc_len;
#endif
};
unsigned long x;