diff options
Diffstat (limited to 'executor/common_linux.h')
| -rw-r--r-- | executor/common_linux.h | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/executor/common_linux.h b/executor/common_linux.h index 682425a3d..2d36b998e 100644 --- a/executor/common_linux.h +++ b/executor/common_linux.h @@ -1981,16 +1981,24 @@ int wait_for_loop(int pid) static void drop_caps(void) { - // Drop CAP_SYS_PTRACE so that test processes can't attach to parent processes. - // Previously it lead to hangs because the loop process stopped due to SIGSTOP. - // Note that a process can always ptrace its direct children, which is enough for testing purposes. struct __user_cap_header_struct cap_hdr = {}; struct __user_cap_data_struct cap_data[2] = {}; cap_hdr.version = _LINUX_CAPABILITY_VERSION_3; cap_hdr.pid = getpid(); if (syscall(SYS_capget, &cap_hdr, &cap_data)) fail("capget failed"); - const int drop = (1 << CAP_SYS_PTRACE); + // Drop CAP_SYS_PTRACE so that test processes can't attach to parent processes. + // Previously it lead to hangs because the loop process stopped due to SIGSTOP. + // Note that a process can always ptrace its direct children, which is enough for testing purposes. + // + // A process with CAP_SYS_NICE can bring kernel down by asking for too high SCHED_DEADLINE priority, + // as the result rcu and other system services that use kernel threads will stop functioning. + // Some parameters for SCHED_DEADLINE should be OK, but we don't have means to enforce + // values of indirect syscall arguments. Peter Zijlstra proposed sysctl_deadline_period_{min,max} + // which could be used to enfore safe limits without droppping CAP_SYS_NICE, but we don't have it yet. + // See the following bug for details: + // https://groups.google.com/forum/#!topic/syzkaller-bugs/G6Wl_PKPIWI + const int drop = (1 << CAP_SYS_PTRACE) | (1 << CAP_SYS_NICE); cap_data[0].effective &= ~drop; cap_data[0].permitted &= ~drop; cap_data[0].inheritable &= ~drop; |