[ Upstream commit 674e2b2479 ]
This command:
# echo foo/bar >/proc/$$/attr/smack/current
gives the task a label 'foo' w/o indication
that label does not match input.
Setting the label with lsm_set_self_attr() syscall
behaves identically.
This occures because:
1) smk_parse_smack() is used to convert input to a label
2) smk_parse_smack() takes only that part from the
beginning of the input that looks like a label.
3) `/' is prohibited in labels, so only "foo" is taken.
(2) is by design, because smk_parse_smack() is used
for parsing strings which are more than just a label.
Silent failure is not a good thing, and there are two
indicators that this was not done intentionally:
(size >= SMK_LONGLABEL) ~> invalid
clause at the beginning of the do_setattr() and the
"Returns the length of the smack label" claim
in the do_setattr() description.
So I fixed this by adding one tiny check:
the taken label length == input length.
Since input length is now strictly controlled,
I changed the two ways of setting label
smack_setselfattr(): lsm_set_self_attr() syscall
smack_setprocattr(): > /proc/.../current
to accommodate the divergence in
what they understand by "input length":
smack_setselfattr counts mandatory \0 into input length,
smack_setprocattr does not.
smack_setprocattr allows various trailers after label
Related changes:
* fixed description for smk_parse_smack
* allow unprivileged tasks validate label syntax.
* extract smk_parse_label_len() from smk_parse_smack()
so parsing may be done w/o string allocation.
* extract smk_import_valid_label() from smk_import_entry()
to avoid repeated parsing.
* smk_parse_smack(): scan null-terminated strings
for no more than SMK_LONGLABEL(256) characters
* smack_setselfattr(): require struct lsm_ctx . flags == 0
to reserve them for future.
Fixes: e114e47377 ("Smack: Simplified Mandatory Access Control Kernel")
Signed-off-by: Konstantin Andreev <andreev@swemel.ru>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
cf008f5bd3