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uprobes/x86: Harden uretprobe syscall trampoline check

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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: ff474a78ce ("uprobe: Add uretprobe syscall to speed up return probe")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Alexei 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
This commit is contained in:
Jiri Olsa 2025-02-12 23:04:33 +01:00 • committed by Ingo Molnar
parent 05763885e3
commit fa6192adc3
3 changed files with 12 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

14
arch/x86/kernel/uprobes.c
View file

@ -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 (regs->ip != trampoline_check_ip())
/* 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;
/* 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));

2
include/linux/uprobes.h
View file

@ -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

2
kernel/events/uprobes.c
View file

@ -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); /* ^^^ */