From nobody Wed Aug 27 07:49:35 2025 X-Original-To: bugs@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4cBcB70zrhz65tN8 for ; Wed, 27 Aug 2025 07:49:35 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R12" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4cBcB70QsVz47kS for ; Wed, 27 Aug 2025 07:49:35 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1756280975; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; 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Wed, 27 Aug 2025 07:49:34 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 57R7nYl3019464 for bugs@FreeBSD.org; Wed, 27 Aug 2025 07:49:34 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 289120] A time-of-check to time-of-use race exists in gpioc_kqread() of GPIO subsystem Date: Wed, 27 Aug 2025 07:49:35 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 14.3-RELEASE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: chenqiuji666@gmail.com X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status bug_severity priority component assigned_to reporter Message-ID: Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated List-Id: Bug reports List-Archive: https://lists.freebsd.org/archives/freebsd-bugs List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-bugs@FreeBSD.org MIME-Version: 1.0 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D289120 Bug ID: 289120 Summary: A time-of-check to time-of-use race exists in gpioc_kqread() of GPIO subsystem Product: Base System Version: 14.3-RELEASE Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: chenqiuji666@gmail.com In gpioc_kqread(), kn->kn_data is computed via number_of_events(), which re= ads evidx_head, evidx_tail, and numevents without synchronization. For example: static size_t number_of_events(struct gpioc_cdevpriv *priv) { if (priv->evidx_head >=3D priv->evidx_tail) return (priv->evidx_head - priv->evidx_tail); else return (priv->numevents + priv->evidx_head - priv->evidx_tail); } Because head/tail may change between the check and the use, the =E2=80=9Che= ad >=3D tail=E2=80=9D test can fail, and the subtraction may overflow. Impact =E2=80=A2 Undefined behavior: signed overflow. =E2=80=A2 Wrong interface semantics: EVFILT_READ kn_data may become a very = large value, leading to bogus copyout values and faulty user decisions (e.g., self-DoS). Suggested fix Snapshot head, tail, and numevents once into local variables and compute fr= om that single snapshot, instead of repeatedly reading shared fields. --=20 You are receiving this mail because: You are the assignee for the bug.=