diff options
| author | Jann Horn | 2019-07-04 20:44:44 +0200 |
|---|---|---|
| committer | Casey Schaufler | 2019-09-04 09:36:57 -0700 |
| commit | 3675f052b43ba51b99b85b073c7070e083f3e6fb (patch) | |
| tree | 17e7be1715228c848eac94d506ce192255a253e8 | |
| parent | 0ecfebd2b52404ae0c54a878c872bb93363ada36 (diff) | |
Smack: Don't ignore other bprm->unsafe flags if LSM_UNSAFE_PTRACE is set
There is a logic bug in the current smack_bprm_set_creds():
If LSM_UNSAFE_PTRACE is set, but the ptrace state is deemed to be
acceptable (e.g. because the ptracer detached in the meantime), the other
->unsafe flags aren't checked. As far as I can tell, this means that
something like the following could work (but I haven't tested it):
- task A: create task B with fork()
- task B: set NO_NEW_PRIVS
- task B: install a seccomp filter that makes open() return 0 under some
conditions
- task B: replace fd 0 with a malicious library
- task A: attach to task B with PTRACE_ATTACH
- task B: execve() a file with an SMACK64EXEC extended attribute
- task A: while task B is still in the middle of execve(), exit (which
destroys the ptrace relationship)
Make sure that if any flags other than LSM_UNSAFE_PTRACE are set in
bprm->unsafe, we reject the execve().
Cc: stable@vger.kernel.org
Fixes: 5663884caab1 ("Smack: unify all ptrace accesses in the smack")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
| -rw-r--r-- | security/smack/smack_lsm.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 4c5e5a438f8b..d8b59480a01c 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -937,7 +937,8 @@ static int smack_bprm_set_creds(struct linux_binprm *bprm) if (rc != 0) return rc; - } else if (bprm->unsafe) + } + if (bprm->unsafe & ~LSM_UNSAFE_PTRACE) return -EPERM; bsp->smk_task = isp->smk_task; |