* [PATCH] keys: Fix description size
@ 2019-08-19 15:02 David Howells
2019-08-19 16:44 ` Linus Torvalds
0 siblings, 1 reply; 2+ messages in thread
From: David Howells @ 2019-08-19 15:02 UTC (permalink / raw)
To: torvalds
Cc: kernel test robot, dhowells, keyrings, linux-security-module,
linux-kernel
The maximum key description size is 4095. Commit f771fde82051
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: f771fde82051 ("keys: Simplify key description management")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/key.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/linux/key.h b/include/linux/key.h
index 91f391cd272e..50028338a4cc 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -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;
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] keys: Fix description size
2019-08-19 15:02 [PATCH] keys: Fix description size David Howells
@ 2019-08-19 16:44 ` Linus Torvalds
0 siblings, 0 replies; 2+ messages in thread
From: Linus Torvalds @ 2019-08-19 16:44 UTC (permalink / raw)
To: David Howells
Cc: kernel test robot, keyrings, LSM List, Linux List Kernel Mailing
On Mon, Aug 19, 2019 at 8:02 AM David Howells <dhowells@redhat.com> wrote:
>
> This can be fixed by simply increasing the size of desc_len in struct
> keyring_index_key to a u16.
Thanks, applied.
Linus
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