Re: [PATCH v3] LSM: use 32 bit compatible data types in LSM syscalls.

[Casey Schaufler <casey@schaufler-ca.com>]

On 3/13/2024 3:37 PM, Paul Moore wrote:
> On Wed, Mar 13, 2024 at 4:07 PM Paul Moore <paul@paul-moore.com> wrote:
>> On Mar 13, 2024 Casey Schaufler <casey@schaufler-ca.com> wrote:
>>> LSM: use 32 bit compatible data types in LSM syscalls.
>>>
>>> Change the size parameters in lsm_list_modules(), lsm_set_self_attr()
>>> and lsm_get_self_attr() from size_t to u32. This avoids the need to
>>> have different interfaces for 32 and 64 bit systems.
>>>
>>> Cc: stable@vger.kernel.org
>>> Fixes: a04a1198088a: ("LSM: syscalls for current process attributes")
>>> Fixes: ad4aff9ec25f: ("LSM: Create lsm_list_modules system call")
>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>> Reported-and-reviewed-by: Dmitry V. Levin <ldv@strace.io>
>>> ---
>>>  include/linux/lsm_hook_defs.h                        |  4 ++--
>>>  include/linux/security.h                             |  8 ++++----
>>>  security/apparmor/lsm.c                              |  4 ++--
>>>  security/lsm_syscalls.c                              | 10 +++++-----
>>>  security/security.c                                  | 12 ++++++------
>>>  security/selinux/hooks.c                             |  4 ++--
>>>  security/smack/smack_lsm.c                           |  4 ++--
>>>  tools/testing/selftests/lsm/common.h                 |  6 +++---
>>>  tools/testing/selftests/lsm/lsm_get_self_attr_test.c | 10 +++++-----
>>>  tools/testing/selftests/lsm/lsm_list_modules_test.c  |  8 ++++----
>>>  tools/testing/selftests/lsm/lsm_set_self_attr_test.c |  6 +++---
>>>  11 files changed, 38 insertions(+), 38 deletions(-)
>> Okay, this looks better, I'm going to merge this into lsm/stable-6.9
>> and put it through the usual automated testing as well as a kselftest
>> run to make sure everything there is still okay.  Assuming all goes
>> well and no one raises any objections, I'll likely send this up to
>> Linus tomorrow.
>>
>> Thanks everyone!
> Unfortunately it looks like we have a kselftest failure (below).  I'm
> pretty sure that this was working at some point, but it's possible I
> missed it when I ran the selftests previously.  I've got to break for
> a personal appt right now, but I'll dig into this later tonight.

In v2:

diff --git a/security/security.c b/security/security.c
index 7035ee35a393..a0f9caf89ae1 100644
--- a/security/security.c
+++ b/security/security.c
@@ -810,7 +810,7 @@ int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, size_t *uctx_len,
 	nctx->ctx_len = val_len;
 	memcpy(nctx->ctx, val, val_len);
 
-	if (copy_to_user(uctx, nctx, nctx_len))
+	if (uctx && copy_to_user(uctx, nctx, nctx_len))
 		rc = -EFAULT;
 
 out:

This addresses the case where NULL is passed in the call to lsm_get_self_attr()
to get the buffer size required.


>
> # timeout set to 45
> # selftests: lsm: lsm_get_self_attr_test
> # TAP version 13
> # 1..6
> # # Starting 6 tests from 1 test cases.
> # #  RUN           global.size_null_lsm_get_self_attr ...
> # #            OK  global.size_null_lsm_get_self_attr
> # ok 1 global.size_null_lsm_get_self_attr
> # #  RUN           global.ctx_null_lsm_get_self_attr ...
> # # lsm_get_self_attr_test.c:49:ctx_null_lsm_get_self_attr:Expected -1 (-1) != r
> c (-1)
> # # ctx_null_lsm_get_self_attr: Test terminated by assertion
> # #          FAIL  global.ctx_null_lsm_get_self_attr
> # not ok 2 global.ctx_null_lsm_get_self_attr
> # #  RUN           global.size_too_small_lsm_get_self_attr ...
> # #            OK  global.size_too_small_lsm_get_self_attr
> # ok 3 global.size_too_small_lsm_get_self_attr
> # #  RUN           global.flags_zero_lsm_get_self_attr ...
> # #            OK  global.flags_zero_lsm_get_self_attr
> # ok 4 global.flags_zero_lsm_get_self_attr
> # #  RUN           global.flags_overset_lsm_get_self_attr ...
> # #            OK  global.flags_overset_lsm_get_self_attr
> # ok 5 global.flags_overset_lsm_get_self_attr
> # #  RUN           global.basic_lsm_get_self_attr ...
> # #            OK  global.basic_lsm_get_self_attr
> # ok 6 global.basic_lsm_get_self_attr
> # # FAILED: 5 / 6 tests passed.
> # # Totals: pass:5 fail:1 xfail:0 xpass:0 skip:0 error:0
> not ok 1 selftests: lsm: lsm_get_self_attr_test # exit=1
>