@@ -45,6 +45,8 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
#define PT_EXITKILL (PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)
#define PT_SUSPEND_SECCOMP (PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT)
+#define PT_SUSPEND_SYSCALL_USER_DISPATCH \
+ (PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH << PT_OPT_FLAG_SHIFT)
extern long arch_ptrace(struct task_struct *child, long request,
unsigned long addr, unsigned long data);
@@ -146,9 +146,13 @@ struct ptrace_rseq_configuration {
/* eventless options */
#define PTRACE_O_EXITKILL (1 << 20)
#define PTRACE_O_SUSPEND_SECCOMP (1 << 21)
+#define PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH (1 << 22)
#define PTRACE_O_MASK (\
- 0x000000ff | PTRACE_O_EXITKILL | PTRACE_O_SUSPEND_SECCOMP)
+ 0x000000ff | \
+ PTRACE_O_EXITKILL | \
+ PTRACE_O_SUSPEND_SECCOMP | \
+ PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)
#include <asm/ptrace.h>
@@ -8,6 +8,7 @@
#include <linux/uaccess.h>
#include <linux/signal.h>
#include <linux/elf.h>
+#include <linux/ptrace.h>
#include <linux/sched/signal.h>
#include <linux/sched/task_stack.h>
@@ -36,6 +37,10 @@ bool syscall_user_dispatch(struct pt_regs *regs)
struct syscall_user_dispatch *sd = ¤t->syscall_dispatch;
char state;
+ if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
+ unlikely(current->ptrace & PT_SUSPEND_SYSCALL_USER_DISPATCH))
+ return false;
+
if (likely(instruction_pointer(regs) - sd->offset < sd->len))
return false;
@@ -370,6 +370,11 @@ static int check_ptrace_options(unsigned long data)
if (data & ~(unsigned long)PTRACE_O_MASK)
return -EINVAL;
+ if (unlikely(data & PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)) {
+ if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTART))
+ return -EINVAL;
+ }
+
if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) {
if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) ||
!IS_ENABLED(CONFIG_SECCOMP))
Adds PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH to ptrace options, and modify Syscall User Dispatch to suspend interception when enabled. This is modeled after the SUSPEND_SECCOMP feature, which suspends SECCOMP interposition. Without doing this, software like CRIU will inject system calls into a process and be intercepted by Syscall User Dispatch, either causing a crash (due to blocked signals) or the delivery of those signals to a ptracer (not the intended behavior). Since Syscall User Dispatch is not a privileged feature, a check for permissions is not required, however attempting to set this option when CONFIG_CHECKPOINT_RESTORE it not supported should be disallowed, as its intended use is checkpoint/resume. Signed-off-by: Gregory Price <gregory.price@memverge.com> --- include/linux/ptrace.h | 2 ++ include/uapi/linux/ptrace.h | 6 +++++- kernel/entry/syscall_user_dispatch.c | 5 +++++ kernel/ptrace.c | 5 +++++ 4 files changed, 17 insertions(+), 1 deletion(-)