On Fri, Jan 17, 2025 at 12:02 AM Masami Hiramatsu [off-list ref] wrote:

On Fri, 17 Jan 2025 02:39:28 +0100
Oleg Nesterov [off-list ref] wrote:

quoted

On 01/16, Eyal Birger wrote:

quoted

Fixes: ff474a78cef5 ("uprobe: Add uretprobe syscall to speed up return probe")
Reported-by: Rafael Buchbinder <redacted>
Link: https://lore.kernel.org/lkml/CAHsH6Gs3Eh8DFU0wq58c_LF8A4_+o6z456J7BidmcVY2AqOnHQ@mail.gmail.com/ (local)
Cc: stable@vger.kernel.org

...

quoted

@@ -1359,6 +1359,11 @@ int __secure_computing(const struct seccomp_data *sd)
    this_syscall = sd ? sd->nr :
            syscall_get_nr(current, current_pt_regs());

+#ifdef CONFIG_X86_64
+   if (unlikely(this_syscall == __NR_uretprobe) && !in_ia32_syscall())
+           return 0;
+#endif

Acked-by: Oleg Nesterov <oleg@redhat.com>


A note for the seccomp maintainers...

I don't know what do you think, but I agree in advance that the very fact this
patch adds "#ifdef CONFIG_X86_64" into __secure_computing() doesn't look nice.

Indeed. in_ia32_syscall() depends arch/x86 too.
We can add an inline function like;

``` uprobes.h
static inline bool is_uprobe_syscall(int syscall)
{
        // arch_is_uprobe_syscall check can be replaced by Kconfig,
        // something like CONFIG_ARCH_URETPROBE_SYSCALL.
#ifdef arch_is_uprobe_syscall
        return arch_is_uprobe_syscall(syscall)
#else
        return false;
#endif
}

and
``` arch/x86/include/asm/uprobes.h
#define arch_is_uprobe_syscall(syscall) \
        (IS_ENABLED(CONFIG_X86_64) && syscall == __NR_uretprobe && !in_ia32_syscall())

Notice it'll need to be enclosed in ifdef CONFIG_X86_64 as __NR_uretprobe
isn't defined otherwise so the IS_ENABLED isn't needed.

quoted

The problem is that we need a simple patch for -stable which fixes the real
problem. We can cleanup this logic later, I think.

Hmm, at least we should make it is_uprobe_syscall() in uprobes.h so that
do not pollute the seccomp subsystem with #ifdef.

I like this approach.

Notice it does add a couple of includes that weren't there before:
- arch/x86/include/asm/uprobes.h would include asm/unistd.h
- seccomp.c would include linux/uprobes.h

So it's a less "trivial" patch... If that's ok I can repost with these
changes.

Eyal.