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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 S966168AbeCSQJd (ORCPT ); Mon, 19 Mar 2018 12:09:33 -0400 Received: from mail-cys01nam02on0131.outbound.protection.outlook.com ([104.47.37.131]:49376 "EHLO NAM02-CY1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S966304AbeCSQJL (ORCPT ); Mon, 19 Mar 2018 12:09:11 -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 4.4 074/167] fix race in drivers/char/random.c:get_reg() Thread-Topic: [PATCH AUTOSEL for 4.4 074/167] fix race in drivers/char/random.c:get_reg() Thread-Index: AQHTv5xM5Yz3JEdzWECzTvJXomKJOA== Date: Mon, 19 Mar 2018 16:06:54 +0000 Message-ID: <20180319160513.16384-74-alexander.levin@microsoft.com> References: <20180319160513.16384-1-alexander.levin@microsoft.com> In-Reply-To: <20180319160513.16384-1-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;DM5PR2101MB0965;7:FfJkYmaieRT+4AvB2I8Bs16+ysw6d8fM6zwtC8WlzC3MRVqWJlBezngiddaSTSBN+yHASHUpOKjz6X/JBCzEaBwaVyGdYN2blSHja129KOnRunSNGLchkRanzoY9pf7HF1HQbtfUxg7IhjIWaFoRufy7pCiWvxYeRt2pjWnXmhjxhB20PJGPEUtlRRklND53nx8oPVKqu5M/7BdwBoqIOquvGPcvsh7r+Q82BeuB2d/W7o9rY+UNZJJD3fvunLIQ;20:LhmoEE4N89iH/YiV1SzmH0WHH+qZK9Y1BjqTQCase8CZfz+LokBOpBDcg/25AfXY3eL04vgHATp7oIo+OCLMsFswzWwxnj9OB1XlZsR8msQvCKVuWab7TR67tgvuAW3W56o2575uOrDuNrENTmOZvHRm7FRDAK1hB1AaGFl8O08= x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 04cb157a-52d9-4b3c-7864-08d58db3ba5b x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7193020);SRVR:DM5PR2101MB0965; 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x-microsoft-antispam-message-info: LfRtvhw9+KPFkZK0mbD2k+ax2D1NMxEBPofyZyiq91gmdtom++B22tO4BR+hr23CddPfY0zxS8HiQR9qcmMxTJlEn6v2zyvXPZ8jwU2uxB3cqtPU1110PDxyW485GOTLya/ciyHyO5wM4NSos0fBInzr885wL8nBiQYVrdBgtOBlimmTHIE0XMqF5Pu77oWadS09aVacSFog2nS3lMVjyD7TuVVPvnKjCZlWmC8DgcmxEmTUwKiKBzoemlTH9xEFbi8zz3IkKqia4AZp1Rwn4JGAkDkWeGbIoICU+OYxcfsnz3ms18wOx9wzbkxpyGs6roIZj56aekq9kU5K57iqUg== 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: 04cb157a-52d9-4b3c-7864-08d58db3ba5b X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Mar 2018 16:06:54.9830 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB0965 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 1822472dffab..29b4218e9b63 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -886,12 +886,16 @@ 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