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| author | Eric W. Biederman <ebiederm@xmission.com> | 2021-10-29 16:14:19 +0200 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2021-11-03 20:09:26 +0100 |
| commit | 00b06da29cf9dc633cdba87acd3f57f4df3fd5c7 (patch) | |
| tree | 03f44557b5bacbc48f8be82435d6bd57312509c6 /include/uapi | |
| parent | signal: Replace force_sigsegv(SIGSEGV) with force_fatal_sig(SIGSEGV) (diff) | |
| download | linux-00b06da29cf9dc633cdba87acd3f57f4df3fd5c7.tar.xz linux-00b06da29cf9dc633cdba87acd3f57f4df3fd5c7.zip | |
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/uapi')
| -rw-r--r-- | include/uapi/asm-generic/signal-defs.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/asm-generic/signal-defs.h b/include/uapi/asm-generic/signal-defs.h index fe929e7b77ca..7572f2f46ee8 100644 --- a/include/uapi/asm-generic/signal-defs.h +++ b/include/uapi/asm-generic/signal-defs.h @@ -45,6 +45,7 @@ #define SA_UNSUPPORTED 0x00000400 #define SA_EXPOSE_TAGBITS 0x00000800 /* 0x00010000 used on mips */ +/* 0x00800000 used for internal SA_IMMUTABLE */ /* 0x01000000 used on x86 */ /* 0x02000000 used on x86 */ /* |