On Sun, Feb 9, 2025 at 2:05 PM Jiri Olsa <jolsa@xxxxxxxxxx> 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 <kees@xxxxxxxxxx> > Cc: Eyal Birger <eyal.birger@xxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Reported-by: Jann Horn <jannh@xxxxxxxxxx> > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> > --- > 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()? > + 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 >
