linux-kernel - [PATCH RESEND] x86/split_lock: Warn for bus locks once for each task

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20250910162126.157894-1-pfalcato@suse.de>
Date: Wed, 10 Sep 2025 17:21:26 +0100
From: Pedro Falcato <pfalcato@...e.de>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org
Cc: "H. Peter Anvin" <hpa@...or.com>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Maksim Davydov <davydov-max@...dex-team.ru>,
	linux-kernel@...r.kernel.org,
	Pedro Falcato <pfalcato@...e.de>
Subject: [PATCH RESEND] x86/split_lock: Warn for bus locks once for each task

Sometimes, it's possible to see long-running services that keep pounding
the bus_lock logic in a long-standing way that does not trigger
ratelimiting, but still floods the dmesg nonetheless, over time.

Fix it by using current->reported_split_lock, which was previously
used for the split_lock handling. In this way, bus_lock #DB's are only
warned once in the dmesg, for each task that hits a bus lock.

Signed-off-by: Pedro Falcato <pfalcato@...e.de>
---
This is already reflected in the documentation for bus lock, as "Warn
once per task and and continues to run.".

Resend since the first mail had accidentally no mailing list in CC.

 arch/x86/kernel/cpu/bus_lock.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bus_lock.c b/arch/x86/kernel/cpu/bus_lock.c
index 981f8b1f0792..71342e6244e3 100644
--- a/arch/x86/kernel/cpu/bus_lock.c
+++ b/arch/x86/kernel/cpu/bus_lock.c
@@ -335,8 +335,11 @@ void handle_bus_lock(struct pt_regs *regs)
 		/* Warn on the bus lock. */
 		fallthrough;
 	case sld_warn:
-		pr_warn_ratelimited("#DB: %s/%d took a bus_lock trap at address: 0x%lx\n",
+		if (!current->reported_split_lock) {
+			pr_warn_ratelimited("#DB: %s/%d took a bus_lock trap at address: 0x%lx\n",
 				    current->comm, current->pid, regs->ip);
+			current->reported_split_lock = 1;
+		}
 		break;
 	case sld_fatal:
 		force_sig_fault(SIGBUS, BUS_ADRALN, NULL);
-- 
2.51.0