Commit fa6192ad authored by Jiri Olsa's avatar Jiri Olsa Committed by Ingo Molnar
Browse files

uprobes/x86: Harden uretprobe syscall trampoline check 

Jann reported a 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:

   https://lore.kernel.org/bpf/202502081235.5A6F352985@keescook/T/#m9d416df341b8fbc11737dacbcd29f0054413cbbf



Though the mmap minimum address restrictions will typically prevent
creating mappings there, let's make sure uretprobe syscall checks
for that.

Fixes: ff474a78 ("uprobe: Add uretprobe syscall to speed up return probe")
Reported-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarKees Cook <kees@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: default avatarAlexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250212220433.3624297-1-jolsa@kernel.org
parent 05763885

arch/x86/kernel/uprobes.c

+9 −5
Original line number Diff line number Diff line
@@ -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));

include/linux/uprobes.h

+2 −0
Original line number Diff line number Diff line
@@ -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

kernel/events/uprobes.c

+1 −1
Original line number Diff line number Diff line
@@ -2169,8 +2169,8 @@ 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); /* ^^^ */