linux-kernel - [PATCHv2 perf/core] uprobes: Harden uretprobe syscall trampoline check

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Message-ID: <20250211111559.2984778-1-jolsa@kernel.org>
Date: Tue, 11 Feb 2025 12:15:59 +0100
From: Jiri Olsa <jolsa@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrii Nakryiko <andrii@...nel.org>
Cc: Kees Cook <kees@...nel.org>,
	Eyal Birger <eyal.birger@...il.com>,
	stable@...r.kernel.org,
	Jann Horn <jannh@...gle.com>,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	linux-api@...r.kernel.org,
	x86@...nel.org,
	bpf@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Deepak Gupta <debug@...osinc.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: [PATCHv2 perf/core] uprobes: Harden uretprobe syscall trampoline check

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/#m9d416df341b8fbc11737dacbcd29f0054413cbbf
Cc: Kees Cook <kees@...nel.org>
Cc: Eyal Birger <eyal.birger@...il.com>
Cc: stable@...r.kernel.org
Fixes: ff474a78cef5 ("uprobe: Add uretprobe syscall to speed up return probe")
Reported-by: Jann Horn <jannh@...gle.com>
Reviewed-by: Oleg Nesterov <oleg@...hat.com>
Reviewed-by: Kees Cook <kees@...nel.org>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
v2 changes:
- adding UPROBE_NO_TRAMPOLINE_VADDR macro (Andrii)
- rebased on top of perf/core

 arch/x86/kernel/uprobes.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 5a952c5ea66b..e8d3c59aa9f7 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -357,19 +357,25 @@ 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);
 }
 
+#define UPROBE_NO_TRAMPOLINE_VADDR ((unsigned long)-1)
+
 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));
-- 
2.48.1