From nobody Tue Apr 7 07:33:06 2026 Received: from mail-oo1-f74.google.com (mail-oo1-f74.google.com [209.85.161.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F28883328F7 for ; Sat, 14 Mar 2026 18:26:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773512780; cv=none; b=tT5wHW66LOWIYs21ZKRGHUkwhTgMsSylDMXyvxZHCTNehsmvwRX5YunP27gYgvhve4ORDIQVtLVg+oCF1SZ8ACAwbMXRdalKpJWjTI7Qvu9j5Hslxszoq1cHJ2EIWN8Bhe3ZXJoM/Ga60YopLRa7xdBlDhEEcFn/Rb5WM6bc36Q= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773512780; c=relaxed/simple; bh=UuFuT0l1KYwYZdB5mWTSbklKSYsWsAcJcG9znNrpxgk=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=TU42d6iYq+ySw9O0wTxNVL5jfARUdV5wWLf0kd4Ap+fSa9TxG0OGoiGnXJPFgJy7fur74NpRYfWz4vpYsRpQxM2EAveZTG+asIyH4fQiZG/ZDQawstv4w9aKaamrWvG8o07jbG67HVT0TRnqsqnb8cFDYuUg11v9DKN/SK0DrIg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--avagin.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=DCOi5CW3; arc=none smtp.client-ip=209.85.161.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--avagin.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="DCOi5CW3" Received: by mail-oo1-f74.google.com with SMTP id 006d021491bc7-67bb7ed941fso50682116eaf.0 for ; Sat, 14 Mar 2026 11:26:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1773512778; x=1774117578; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=PMMxLaT3jAMxP/Zxo0zPx+DmGMBLvPcOcDOLOaYp0w8=; b=DCOi5CW3dEjZx5Swse+E0VTCvz+uWSKu8QAqycAkNNhvMPgz8rjPyKcKRkh3iWMTL0 tj1EMSKip3m+MK434+pV4vcU5pnUaz6AiLNMk+PKFauP5A2lWXuTyl+hu8zyShjzTFlX 8MKqg2bvXLUsl8fwyOADysS5PIXY91uWJDTHBC5o/YH5PpghflSTnQSUZIaGdBjmxWDk MCVyKjsUgpKGFv5qpZmtsEk1zzmNpe3vKR3xuCjX8ETZ4BVccc1QlXGGXuiHJLVpduIJ kkIW/3al4YOeNAruRE2PcLrxtOzRhVtpMic/5Xdtf+WWD3MB6CSk15i4sAmF8ram7eJT OGig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773512778; x=1774117578; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=PMMxLaT3jAMxP/Zxo0zPx+DmGMBLvPcOcDOLOaYp0w8=; b=dPjJMCrlxSe4hcHHq7j/GCpSIbAFXemLpJTDoIZA+BsQDymOPxupdZcsLPmCJCanu6 5b8cx3xvj6vGza1XlhU5dr4VRSSXyU3HQqI0VbRsjRhdDbBUG1J53P7Cx7Qp0yogGb1p a9DOXbyYrOsoOXvk5a1kR4AbeHiTkQJwLSl4+RleY+vIJzvjNSnGGlaaqRBJCpbRt9P/ RdoVBzka13EwHR1ruQOdrPDc/oAQajrfeplZX6EEU8lPAvmOOEfTA+ceL0F5U6IrIiDg Ut7D5r4gDjgiIr4E6KbRKI+H1QCH4KK2oUpIK1gda6V+L8fmCeewQjp10p2BlNksZ+yR WYpQ== X-Forwarded-Encrypted: i=1; AJvYcCVyfXyiCa/HO6O/jIp6AHX2aZT4U1iwShJ/T1Kv85jfvanRxYYjJVi7Zfm8g2GgDS+l/kIua/QjwaTZkDU=@vger.kernel.org X-Gm-Message-State: AOJu0Yz6KtBnoKY0jLIYXl7/cJQqGW/K5dEL04xro0mGCuyLX1TsDG73 X7UJ1LQVYipJyb5vOKbmKBcZOGk3AbCFtjy/e6vM4Iqv+ztiJVPYvx2+YLglHKaI/g9MxwNcr4D stIq/BA== X-Received: from ilbdr11.prod.google.com ([2002:a05:6e02:3f0b:b0:4f7:185c:4f47]) (user=avagin job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6820:4de4:b0:67b:ef7f:5c37 with SMTP id 006d021491bc7-67bef7f5dccmr1163848eaf.54.1773512777702; Sat, 14 Mar 2026 11:26:17 -0700 (PDT) Date: Sat, 14 Mar 2026 18:26:07 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.53.0.851.ga537e3e6e9-goog Message-ID: <20260314182607.3343346-1-avagin@google.com> Subject: [PATCH] locking/rwsem: Fix logic error in rwsem_del_waiter() From: Andrei Vagin To: "Matthew Wilcox (Oracle)" , Peter Zijlstra Cc: Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , linux-kernel@vger.kernel.org, Andrei Vagin , syzbot+3d2ff92c67127d337463@syzkaller.appspotmail.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Commit 1ea4b473504b ("locking/rwsem: Remove the list_head from struct rw_semaphore") introduced a logic error in rwsem_del_waiter(). The root cause of this issue is an inconsistency in the return values of __rwsem_del_waiter() and rwsem_del_waiter(). Specifically, __rwsem_del_waiter() returns true when the wait list becomes empty, whereas rwsem_del_waiter() is supposed to return true if the wait list is NOT empty. This caused a null pointer dereference in rwsem_mark_wake() because it was being called when sem->first_waiter was NULL. Cc: Matthew Wilcox (Oracle) Reported-by: syzbot+3d2ff92c67127d337463@syzkaller.appspotmail.com Tested-by: syzbot+3d2ff92c67127d337463@syzkaller.appspotmail.com Fixes: 1ea4b473504b ("locking/rwsem: Remove the list_head from struct rw_se= maphore") Signed-off-by: Andrei Vagin --- kernel/locking/rwsem.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index ba4cb74de064..bf647097369c 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -370,7 +370,7 @@ bool __rwsem_del_waiter(struct rw_semaphore *sem, struc= t rwsem_waiter *waiter) { if (list_empty(&waiter->list)) { sem->first_waiter =3D NULL; - return true; + return false; } =20 if (sem->first_waiter =3D=3D waiter) { @@ -379,7 +379,7 @@ bool __rwsem_del_waiter(struct rw_semaphore *sem, struc= t rwsem_waiter *waiter) } list_del(&waiter->list); =20 - return false; + return true; } =20 /* --=20 2.53.0.851.ga537e3e6e9-goog