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author | Jann Horn <jannh@google.com> | 2019-07-04 20:44:44 +0200 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-10-07 18:59:39 +0200 |
commit | 73cf33180fd5786b83fb1fd469a41c8293f4c7ca (patch) | |
tree | 47529fad04c74186cace27bd3d956da9a16d0db1 | |
parent | e4875cfb207fd2e4ca0edd5edc3bf5a4b4f060b8 (diff) | |
download | linux-stable-73cf33180fd5786b83fb1fd469a41c8293f4c7ca.tar.gz linux-stable-73cf33180fd5786b83fb1fd469a41c8293f4c7ca.tar.bz2 linux-stable-73cf33180fd5786b83fb1fd469a41c8293f4c7ca.zip |
Smack: Don't ignore other bprm->unsafe flags if LSM_UNSAFE_PTRACE is set
commit 3675f052b43ba51b99b85b073c7070e083f3e6fb upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-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 5c9fc8ba6e57..4777e3eb3ae8 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; |