Andrea Righi <andrea.righi@xxxxxxxxxxxxx> writes: > On Fri, Oct 29, 2021 at 10:09:04AM -0500, Eric W. Biederman wrote: >> >> 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@xxxxxxxxxxxxxxxx >> [2] https://lkml.kernel.org/r/202110281136.5CE65399A7@keescook >> Cc: stable@xxxxxxxxxxxxxxx >> Fixes: 307d522f5eb8 ("signal/seccomp: Refactor seccomp signal and coredump generation") >> Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> >> --- > > FWIW I've tested this patch and I confirm that it fixes the failure that > I reported with the seccomp_bpf selftest. > > Tested-by: Andrea Righi <andrea.righi@xxxxxxxxxxxxx> Sigh. Except for the extra 0 in the definition of SA_IMMUTABLE that caused it to conflict with the x86 specific signal numbers. Eric
