diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2021-10-29 09:14:19 -0500 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2021-11-03 14:09:26 -0500 |
| commit | 00b06da29cf9dc633cdba87acd3f57f4df3fd5c7 (patch) | |
| tree | 03f44557b5bacbc48f8be82435d6bd57312509c6 /include/linux/signal_types.h | |
| parent | e21294a7aaae32c5d7154b187113a04db5852e37 (diff) | |
signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed
As Andy pointed out that there are races between
force_sig_info_to_task and sigaction[1] when force_sig_info_task. As
Kees discovered[2] ptrace is also able to change these signals.
In the case of seeccomp killing a process with a signal it is a
security violation to allow the signal to be caught or manipulated.
Solve this problem by introducing a new flag SA_IMMUTABLE that
prevents sigaction and ptrace from modifying these forced signals.
This flag is carefully made kernel internal so that no new ABI is
introduced.
Longer term I think this can be solved by guaranteeing short circuit
delivery of signals in this case. Unfortunately reliable and
guaranteed short circuit delivery of these signals is still a ways off
from being implemented, tested, and merged. So I have implemented a much
simpler alternative for now.
[1] https://lkml.kernel.org/r/b5d52d25-7bde-4030-a7b1-7c6f8ab90660@www.fastmail.com
[2] https://lkml.kernel.org/r/202110281136.5CE65399A7@keescook
Cc: stable@vger.kernel.org
Fixes: 307d522f5eb8 ("signal/seccomp: Refactor seccomp signal and coredump generation")
Tested-by: Andrea Righi <andrea.righi@canonical.com>
Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'include/linux/signal_types.h')
| -rw-r--r-- | include/linux/signal_types.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/signal_types.h b/include/linux/signal_types.h index 34cb28b8f16c..a70b2bdbf4d9 100644 --- a/include/linux/signal_types.h +++ b/include/linux/signal_types.h @@ -70,6 +70,9 @@ struct ksignal { int sig; }; +/* Used to kill the race between sigaction and forced signals */ +#define SA_IMMUTABLE 0x00800000 + #ifndef __ARCH_UAPI_SA_FLAGS #ifdef SA_RESTORER #define __ARCH_UAPI_SA_FLAGS SA_RESTORER |