On Wed, Feb 12, 2025 at 01:05:09PM +0900, Masami Hiramatsu wrote:
On Tue, 11 Feb 2025 17:59:41 +0100 Oleg Nesterov oleg@redhat.com wrote:
On 02/11, Alexei Starovoitov wrote:
+#define UPROBE_NO_TRAMPOLINE_VADDR ((unsigned long)-1)
If you respin anyway maybe use ~0UL instead? In the above and in uprobe_get_trampoline_vaddr(), since
unsigned long trampoline_vaddr = -1;
... or -1ul in both cases.
I agree, UPROBE_NO_TRAMPOLINE_VADDR has a single user, looks a bit strange...
I think both this function and uprobe_get_trampoline_vaddr() should use the same macro as a token. (and ~0UL is a bit more comfortable for me too :) )
unsigned long uprobe_get_trampoline_vaddr(void) { struct xol_area *area; unsigned long trampoline_vaddr = -1;
sounds good, I'll send new version with change below if there are no objections
thanks, jirka
--- diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c index 5a952c5ea66b..015b2a6bac11 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 == 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)); diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h index b1df7d792fa1..a6bec560bdbc 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 2ca797cbe465..e8af2f75b094 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2160,8 +2160,8 @@ 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); /* ^^^ */