linux-kernel - [PATCH v11 03/14] arm64: ptrace: Move rseq_syscall() before audit_syscall

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20260128031934.3906955-4-ruanjinjie@huawei.com>
Date: Wed, 28 Jan 2026 11:19:23 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: <catalin.marinas@....com>, <will@...nel.org>, <oleg@...hat.com>,
	<tglx@...utronix.de>, <peterz@...radead.org>, <luto@...nel.org>,
	<shuah@...nel.org>, <kees@...nel.org>, <wad@...omium.org>,
	<kevin.brodsky@....com>, <deller@....de>, <akpm@...ux-foundation.org>,
	<charlie@...osinc.com>, <ldv@...ace.io>, <mark.rutland@....com>,
	<anshuman.khandual@....com>, <song@...nel.org>, <ryan.roberts@....com>,
	<thuth@...hat.com>, <ada.coupriediaz@....com>, <broonie@...nel.org>,
	<pengcan@...inos.cn>, <liqiang01@...inos.cn>, <kmal@...k.li>,
	<dvyukov@...gle.com>, <reddybalavignesh9979@...il.com>,
	<richard.weiyang@...il.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>
CC: <ruanjinjie@...wei.com>
Subject: [PATCH v11 03/14] arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()

commit a9f3a74a29af ("entry: Provide generic syscall exit function")
introduce generic syscall exit function and call rseq_syscall()
before audit_syscall_exit() and arch_syscall_exit_tracehook().

And commit b74406f37737 ("arm: Add syscall detection for restartable
sequences") add rseq support for arm32, which also call rseq_syscall()
before audit_syscall_exit() and tracehook_report_syscall().

However, commit 409d5db49867c ("arm64: rseq: Implement backend rseq
calls and select HAVE_RSEQ") implement arm64 rseq and call
rseq_syscall() after audit_syscall_exit() and tracehook_report_syscall().
So compared to the generic entry and arm32 code, arm64 calls
rseq_syscall() a bit later.

But as commit b74406f37737 ("arm: Add syscall detection for restartable
sequences") said, syscalls are not allowed inside restartable sequences,
so should call rseq_syscall() at the very beginning of system call
exiting path for CONFIG_DEBUG_RSEQ=y kernel. This could help us to detect
whether there is a syscall issued inside restartable sequences.

As for the impact of raising SIGSEGV via rseq_syscall(), it makes no
practical difference to signal delivery because signals are processed
in arm64_exit_to_user_mode() at the very end.

As for the "regs", rseq_syscall() only checks and update
instruction_pointer(regs), ptrace can not modify the "pc" on syscall exit
path but 'only changes the return value', so calling rseq_syscall()
before or after ptrace_report_syscall_exit() makes no difference.

And audit_syscall_exit() only checks the return value (x0 for arm64),
so calling rseq_syscall() before or after audit syscall exit makes
no difference. trace_sys_exit() only uses syscallno and the return value,
so calling rseq_syscall() before or after trace_sys_exit() also makes
no difference.

In preparation for moving arm64 over to the generic entry code, move
rseq_syscall() ahead before audit_syscall_exit().

No functional changes.

Reviewed-by: Kevin Brodsky <kevin.brodsky@....com>
Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
---
 arch/arm64/kernel/ptrace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 9f9aa3087c09..785280c76317 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2443,6 +2443,8 @@ int syscall_trace_enter(struct pt_regs *regs, unsigned long flags)

 void syscall_trace_exit(struct pt_regs *regs, unsigned long flags)
 {
+	rseq_syscall(regs);
+
 	audit_syscall_exit(regs);

 	if (flags & _TIF_SYSCALL_TRACEPOINT)
@@ -2450,8 +2452,6 @@ void syscall_trace_exit(struct pt_regs *regs, unsigned long flags)

 	if (flags & (_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP))
 		report_syscall_exit(regs);
-
-	rseq_syscall(regs);
 }

 /*
-- 
2.34.1