linux-kernel - [PATCH v2] auditsc: Implement a workaround for a GCC bug triggered by task comm changes

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Message-Id: <20241205021100.86390-1-laoar.shao@gmail.com>
Date: Thu,  5 Dec 2024 10:11:00 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: paul@...l-moore.com,
	keescook@...omium.org
Cc: qiuxu.zhuo@...el.com,
	rostedt@...dmis.org,
	lkp@...el.com,
	audit@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yafang shao <laoar.shao@...il.com>,
	Kees Cook <kees@...nel.org>
Subject: [PATCH v2] auditsc: Implement a workaround for a GCC bug triggered by task comm changes

From: Yafang shao <laoar.shao@...il.com>

A build failure has been reported with the following details:

   In file included from include/linux/string.h:390,
                    from include/linux/bitmap.h:13,
                    from include/linux/cpumask.h:12,
                    from include/linux/smp.h:13,
                    from include/linux/lockdep.h:14,
                    from include/linux/spinlock.h:63,
                    from include/linux/wait.h:9,
                    from include/linux/wait_bit.h:8,
                    from include/linux/fs.h:6,
                    from kernel/auditsc.c:37:
   In function 'sized_strscpy',
       inlined from '__audit_ptrace' at kernel/auditsc.c:2732:2:
>> include/linux/fortify-string.h:293:17: error: call to '__write_overflow' declared with attribute error: detected write beyond size of object (1st parameter)
     293 |                 __write_overflow();
         |                 ^~~~~~~~~~~~~~~~~~
   In function 'sized_strscpy',
       inlined from 'audit_signal_info_syscall' at kernel/auditsc.c:2759:3:
>> include/linux/fortify-string.h:293:17: error: call to '__write_overflow' declared with attribute error: detected write beyond size of object (1st parameter)
     293 |                 __write_overflow();
         |                 ^~~~~~~~~~~~~~~~~~

The issue appears to be a GCC bug, though the root cause remains
unclear at this time. For now, let's implement a workaround.

A bug report has also been filed with GCC [0].

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117912 [0]

Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410171420.1V00ICVG-lkp@intel.com/
Reported-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Closes: https://lore.kernel.org/all/20241128182435.57a1ea6f@gandalf.local.home/
Reported-by: "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>
Closes: https://lore.kernel.org/all/CY8PR11MB71348E568DBDA576F17DAFF389362@CY8PR11MB7134.namprd11.prod.outlook.com/
Originally-by: Kees Cook <kees@...nel.org>
Link: https://lore.kernel.org/linux-hardening/202410171059.C2C395030@keescook/
Signed-off-by: Yafang shao <laoar.shao@...il.com>
Tested-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/auditsc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

v1->2: Add the link of the GCC bug report

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 279ba5c420a4..561d96affe9f 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2728,8 +2728,8 @@ void __audit_ptrace(struct task_struct *t)
 	context->target_auid = audit_get_loginuid(t);
 	context->target_uid = task_uid(t);
 	context->target_sessionid = audit_get_sessionid(t);
-	security_task_getlsmprop_obj(t, &context->target_ref);
 	strscpy(context->target_comm, t->comm);
+	security_task_getlsmprop_obj(t, &context->target_ref);
 }
 
 /**
@@ -2755,8 +2755,8 @@ int audit_signal_info_syscall(struct task_struct *t)
 		ctx->target_auid = audit_get_loginuid(t);
 		ctx->target_uid = t_uid;
 		ctx->target_sessionid = audit_get_sessionid(t);
-		security_task_getlsmprop_obj(t, &ctx->target_ref);
 		strscpy(ctx->target_comm, t->comm);
+		security_task_getlsmprop_obj(t, &ctx->target_ref);
 		return 0;
 	}
 
-- 
2.43.5