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); /* ^^^ */
On Wed, 12 Feb 2025 23:04:33 +0100 Jiri Olsa jolsa@kernel.org wrote:
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
Looks good to me.
Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org
Thank you,
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); /* ^^^ */ -- 2.48.1
On Wed, Feb 12, 2025 at 2:04 PM Jiri Olsa jolsa@kernel.org wrote:
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.
It would be a layering violation, but we could perhaps do better here:
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;
Instead of SIGILL, perhaps this should do the seccomp action? So the logic in seccomp would be (sketchily, with some real mode1 mess):
if (is_a_real_uretprobe()) skip seccomp;
where is_a_real_uretprobe() is only true if the nr and arch match uretprobe *and* the address is right.
--Andy
(sorry for the HTML spam)
On Wed, Feb 12, 2025 at 5:37 PM Andy Lutomirski luto@kernel.org wrote:
On Wed, Feb 12, 2025 at 2:04 PM Jiri Olsa jolsa@kernel.org wrote:
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.
It would be a layering violation, but we could perhaps do better here:
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;Instead of SIGILL, perhaps this should do the seccomp action? So the logic in seccomp would be (sketchily, with some real mode1 mess):
if (is_a_real_uretprobe()) skip seccomp;
where is_a_real_uretprobe() is only true if the nr and arch match uretprobe *and* the address is right.
Why would it make sense to rely on CONFIG_SECCOMP for this check? seems this check should be done regardless of seccomp.
Or maybe I missed something in the suggestion.
Eyal.
--Andy
On Wed, Feb 12, 2025 at 05:37:11PM -0800, Andy Lutomirski wrote:
On Wed, Feb 12, 2025 at 2:04 PM Jiri Olsa jolsa@kernel.org wrote:
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.
It would be a layering violation, but we could perhaps do better here:
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;Instead of SIGILL, perhaps this should do the seccomp action? So the logic in seccomp would be (sketchily, with some real mode1 mess):
if (is_a_real_uretprobe()) skip seccomp;
IIUC you want to move the address check earlier to the seccomp path.. with the benefit that we would kill not allowed caller sooner?
jirka
where is_a_real_uretprobe() is only true if the nr and arch match uretprobe *and* the address is right.
--Andy
On Thu, Feb 13, 2025 at 1:16 AM Jiri Olsa olsajiri@gmail.com wrote:
On Wed, Feb 12, 2025 at 05:37:11PM -0800, Andy Lutomirski wrote:
On Wed, Feb 12, 2025 at 2:04 PM Jiri Olsa jolsa@kernel.org wrote:
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.
It would be a layering violation, but we could perhaps do better here:
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;Instead of SIGILL, perhaps this should do the seccomp action? So the logic in seccomp would be (sketchily, with some real mode1 mess):
if (is_a_real_uretprobe()) skip seccomp;
IIUC you want to move the address check earlier to the seccomp path.. with the benefit that we would kill not allowed caller sooner?
The benefit would be that seccomp users that want to do something other than killing a process (returning an error code, getting notified, etc) could retain that functionality without the new automatic hole being poked for uretprobe() in cases where uprobes aren't in use or where the calling address doesn't match the uprobe trampoline. IOW it would reduce the scope to which we're making seccomp behave unexpectedly.
jirka
where is_a_real_uretprobe() is only true if the nr and arch match uretprobe *and* the address is right.
--Andy
linux-stable-mirror@lists.linaro.org
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Andy Lutomirski -
Eyal Birger -
Jiri Olsa -
Jiri Olsa -
Masami Hiramatsu