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x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=microsoft.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031426AbeCSVSb (ORCPT ); Mon, 19 Mar 2018 17:18:31 -0400 Received: from mail-by2nam03on0105.outbound.protection.outlook.com ([104.47.42.105]:9497 "EHLO NAM03-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965270AbeCSQBA (ORCPT ); Mon, 19 Mar 2018 12:01:00 -0400 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Michael Schmitz , Theodore Ts'o , Sasha Levin Subject: [PATCH AUTOSEL for 4.9 107/281] fix race in drivers/char/random.c:get_reg() Thread-Topic: [PATCH AUTOSEL for 4.9 107/281] fix race in drivers/char/random.c:get_reg() Thread-Index: AQHTv5tVAuFit4TtTUWj2iUSZejoWg== Date: Mon, 19 Mar 2018 15:59:59 +0000 Message-ID: <20180319155742.13731-107-alexander.levin@microsoft.com> References: <20180319155742.13731-1-alexander.levin@microsoft.com> In-Reply-To: <20180319155742.13731-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;DM5PR2101MB1031;7:U18D8EG+4o9bRfU66UZKnHeDdWr9JzmnEdf6jLFGZWCzsru/jE6sTV7dmm5ClAi/jlgEPdo/imWYTLvAOoP0CNEKuAnMnfPv27aZLD4oA7YQW+HVeI68jUYcoErPXGbd8EKwSXQBl1kO09DIm/ljjq/6yLLhNaabpCKVXeYLJcqC7oGZ2I1F5AuZEad1iGcfYLR6dFujHLK+6opQMyJ8Hbv6Nk+h99GFOU9lMocjibcaZX/gr+fDJG3xLGg8tT+Y;20:AwOxp2vn2Ypz0gn6oSkZ7MDO/WnB1tthoF8M3Uev7FqY/Z0t3YdjQJ7zOq0QJAZM0DuzoUpFT2tDJGTUthFZ7gyAYeSFwU9QVpcSH58ULue1LoxTmPzFg1wyrftx+Vo02oOUtwk4bEU6wbAcu1NNIC/Dhgpocozp+sncgz7H84g= x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 12e16c7e-ddb6-4f40-e02d-08d58db2950a x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7193020);SRVR:DM5PR2101MB1031; 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x-microsoft-antispam-message-info: nEVNoedU2Qha2j4NMJdgaejk6Qkd6altdTd7KZ4mtsgzc2w25wSbbqhtTVkwjk+pA74a0Q5cGWoZSHMnsNjg36owxXdoj7bNVhEJDM7PvpXNA6zUiEQVf+UgiNpwweMECMDD16X7F316wH2y31Pz+XqkzJ9g2YlA2SAd5TJT7YwGoJW0Yjdtv9ETRTha7aqT1m6ArvZXTzA9HcFNYQMsLlxGfVipwB1wumYAfdApaJelPbijkqT6+FeZ7QPp3YDZcLeS+YNjj1CglFnuO3OsYjMd/gbUSP5M+6Hgpwt5Ldj1Yx3me2WF2smPJr9FLQZB4SpKddlOiSB7SrdscocUJA== spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: 12e16c7e-ddb6-4f40-e02d-08d58db2950a X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Mar 2018 16:00:00.0126 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB1031 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Michael Schmitz [ Upstream commit 9dfa7bba35ac08a63565d58c454dccb7e1bb0a08 ] get_reg() can be reentered on architectures with prioritized interrupts (m68k in this case), causing f->reg_index to be incremented after the range check. Out of bounds memory access past the pt_regs struct results. This will go mostly undetected unless access is beyond end of memory. Prevent the race by disabling interrupts in get_reg(). Tested on m68k (Atari Falcon, and ARAnyM emulator). Kudos to Geert Uytterhoeven for helping to trace this race. Signed-off-by: Michael Schmitz Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- drivers/char/random.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 08d1dd58c0d2..23f3fb45ff07 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1115,12 +1115,16 @@ static void add_interrupt_bench(cycles_t start) static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs) { __u32 *ptr =3D (__u32 *) regs; + unsigned long flags; =20 if (regs =3D=3D NULL) return 0; + local_irq_save(flags); if (f->reg_idx >=3D sizeof(struct pt_regs) / sizeof(__u32)) f->reg_idx =3D 0; - return *(ptr + f->reg_idx++); + ptr +=3D f->reg_idx++; + local_irq_restore(flags); + return *ptr; } =20 void add_interrupt_randomness(int irq, int irq_flags) --=20 2.14.1