On Mon, Feb 10, 2025 at 09:26:53AM -0800, Andrii Nakryiko wrote: > On Sun, Feb 9, 2025 at 2:05 PM Jiri Olsa <jo...@kernel.org> wrote: > > > > Jann reported [1] possible issue when trampoline_check_ip returns > > address near the bottom of the address space that is allowed to > > call into the syscall if uretprobes are not set up. > > > > Though the mmap minimum address restrictions will typically prevent > > creating mappings there, let's make sure uretprobe syscall checks > > for that. > > > > [1] > > https://lore.kernel.org/bpf/202502081235.5A6F352985@keescook/T/#m9d416df341b8fbc11737dacbcd29f0054413cbbf > > Cc: Kees Cook <k...@kernel.org> > > Cc: Eyal Birger <eyal.bir...@gmail.com> > > Cc: sta...@vger.kernel.org > > Reported-by: Jann Horn <ja...@google.com> > > Signed-off-by: Jiri Olsa <jo...@kernel.org> > > --- > > arch/x86/kernel/uprobes.c | 14 +++++++++----- > > 1 file changed, 9 insertions(+), 5 deletions(-) > > > > diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c > > index 5a952c5ea66b..109d6641a1b3 100644 > > --- a/arch/x86/kernel/uprobes.c > > +++ b/arch/x86/kernel/uprobes.c > > @@ -357,19 +357,23 @@ void *arch_uprobe_trampoline(unsigned long *psize) > > return &insn; > > } > > > > -static unsigned long trampoline_check_ip(void) > > +static unsigned long trampoline_check_ip(unsigned long tramp) > > { > > - unsigned long tramp = uprobe_get_trampoline_vaddr(); > > - > > return tramp + (uretprobe_syscall_check - > > uretprobe_trampoline_entry); > > } > > > > SYSCALL_DEFINE0(uretprobe) > > { > > struct pt_regs *regs = task_pt_regs(current); > > - unsigned long err, ip, sp, r11_cx_ax[3]; > > + unsigned long err, ip, sp, r11_cx_ax[3], tramp; > > + > > + /* If there's no trampoline, we are called from wrong place. */ > > + tramp = uprobe_get_trampoline_vaddr(); > > + if (tramp == -1) > > slight nit: mixing -1 and unsigned long looks sloppy. Maybe let's add > something like > > #define UPROBE_NO_TRAMPOLINE_VADDR ((unsigned long)-1) > > and return that from uprobe_get_trampoline_vaddr()?
ok, will add that thanks, jirka > > > + goto sigill; > > > > - if (regs->ip != trampoline_check_ip()) > > + /* Make sure the ip matches the only allowed sys_uretprobe caller. > > */ > > + if (regs->ip != trampoline_check_ip(tramp)) > > goto sigill; > > > > err = copy_from_user(r11_cx_ax, (void __user *)regs->sp, > > sizeof(r11_cx_ax)); > > -- > > 2.48.1 > >
