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seccomp: kill process instead of thread for unknown actions

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Asynchronous termination of a thread outside of the userspace thread
library's knowledge is an unsafe operation that leaves the process in
an inconsistent, corrupt, and possibly unrecoverable state. In order
to make new actions that may be added in the future safe on kernels
not aware of them, change the default action from
SECCOMP_RET_KILL_THREAD to SECCOMP_RET_KILL_PROCESS.

Signed-off-by: Rich Felker <dalias@libc.org>
Link: https://lore.kernel.org/r/20200829015609.GA32566@brightrain.aerifal.cx
[kees: Fixed up coredump selection logic to match]
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Rich Felker 2020-08-28 21:56:13 -04:00 committed by Kees Cook
parent e839317900
commit 4d671d922d
1 changed files with 4 additions and 4 deletions
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8
kernel/seccomp.c
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@ -1020,7 +1020,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
default:
seccomp_log(this_syscall, SIGSYS, action, true);
/* Dump core only if this is the last remaining thread. */
if (action == SECCOMP_RET_KILL_PROCESS ||
if (action != SECCOMP_RET_KILL_THREAD ||
get_nr_threads(current) == 1) {
kernel_siginfo_t info;
@ -1030,10 +1030,10 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
seccomp_init_siginfo(&info, this_syscall, data);
do_coredump(&info);
}
if (action == SECCOMP_RET_KILL_PROCESS)
do_group_exit(SIGSYS);
else
if (action == SECCOMP_RET_KILL_THREAD)
do_exit(SIGSYS);
else
do_group_exit(SIGSYS);
}
unreachable();