On Wed, Jan 15, 2025 at 10:40 AM Oleg Nesterov [off-list ref] wrote:

On 01/15, Alexei Starovoitov wrote:

quoted

On Wed, Jan 15, 2025 at 7:06 AM Oleg Nesterov [off-list ref] wrote:

quoted

Or we can change __secure_computing() to do nothing if
this_syscall == __NR_uretprobe.

I think that's the best way forward.
seccomp already allowlists sigreturn syscall.

Only if SECCOMP_MODE_STRICT. But it won't help if we add __NR_uretprobe
into into mode1_syscalls/mode1_syscalls_32.

SECCOMP_MODE_FILTER can do anything. Just I guess nobody tries to offend
sigreturn for obvious reasons.

But yes, perhaps we do not have a better solution.

Indeed - doing the check in __secure_computing_strict() doesn't seem to be
enough.

In __secure_computing(), i.e. the below hack it works.

Eyal.

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 385d48293a5f..5739482036ce 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c

@@ -1359,6 +1359,9 @@ int __secure_computing(const struct seccomp_data *sd)
        this_syscall = sd ? sd->nr :
                syscall_get_nr(current, current_pt_regs());

+       if (this_syscall == __NR_uretprobe)
+               return 0;
+
        switch (mode) {
        case SECCOMP_MODE_STRICT:
                __secure_computing_strict(this_syscall);  /* may call do_exit */