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 Fixes: ff474a78cef5 ("uprobe: Add uretprobe syscall to speed up return probe") Reported-by: Jann Horn <jannh@xxxxxxxxxx> Reviewed-by: Oleg Nesterov <oleg@xxxxxxxxxx> Reviewed-by: Kees Cook <kees@xxxxxxxxxx> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> --- v2 changes: - adding UPROBE_NO_TRAMPOLINE_VADDR macro (Andrii) - rebased on top of perf/core arch/x86/kernel/uprobes.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c index 5a952c5ea66b..e8d3c59aa9f7 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -357,19 +357,25 @@ 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); } +#define UPROBE_NO_TRAMPOLINE_VADDR ((unsigned long)-1) + 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 == UPROBE_NO_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
