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/#m9d416df341b... Cc: Kees Cook kees@kernel.org Cc: Eyal Birger eyal.birger@gmail.com Cc: stable@vger.kernel.org Fixes: ff474a78cef5 ("uprobe: Add uretprobe syscall to speed up return probe") Acked-by: Andrii Nakryiko andrii@kernel.org Reported-by: Jann Horn jannh@google.com Reviewed-by: Oleg Nesterov oleg@redhat.com Reviewed-by: Kees Cook kees@kernel.org Signed-off-by: Jiri Olsa jolsa@kernel.org --- v3 changes: - used ~0UL instead of -1 [Alexei] - used UPROBE_NO_TRAMPOLINE_VADDR in uprobe_get_trampoline_vaddr [Masami] - added unlikely [Andrii] - I kept the review/ack tags, because I think the change is basically the same, please scream otherwise
arch/x86/kernel/uprobes.c | 14 +++++++++----- include/linux/uprobes.h | 2 ++ kernel/events/uprobes.c | 2 +- 3 files changed, 12 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c index 5a952c5ea66b..9194695662b2 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 (unlikely(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 (unlikely(regs->ip != trampoline_check_ip(tramp))) goto sigill;
err = copy_from_user(r11_cx_ax, (void __user *)regs->sp, sizeof(r11_cx_ax)); diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h index a40efdda9052..2e46b69ff0a6 100644 --- a/include/linux/uprobes.h +++ b/include/linux/uprobes.h @@ -39,6 +39,8 @@ struct page;
#define MAX_URETPROBE_DEPTH 64
+#define UPROBE_NO_TRAMPOLINE_VADDR (~0UL) + struct uprobe_consumer { /* * handler() can return UPROBE_HANDLER_REMOVE to signal the need to diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 597b9e036e5f..c5d6307bc5bc 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2156,8 +2156,8 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags) */ unsigned long uprobe_get_trampoline_vaddr(void) { + unsigned long trampoline_vaddr = UPROBE_NO_TRAMPOLINE_VADDR; struct xol_area *area; - unsigned long trampoline_vaddr = -1;
/* Pairs with xol_add_vma() smp_store_release() */ area = READ_ONCE(current->mm->uprobes_state.xol_area); /* ^^^ */