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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 S934685AbeCSQlD (ORCPT ); Mon, 19 Mar 2018 12:41:03 -0400 Received: from mail-cys01nam02on0101.outbound.protection.outlook.com ([104.47.37.101]:1938 "EHLO NAM02-CY1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S966839AbeCSQM6 (ORCPT ); Mon, 19 Mar 2018 12:12:58 -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 3.18 044/102] fix race in drivers/char/random.c:get_reg() Thread-Topic: [PATCH AUTOSEL for 3.18 044/102] fix race in drivers/char/random.c:get_reg() Thread-Index: AQHTv50SKnpWhYnAQUCZrzeeMQkI+w== Date: Mon, 19 Mar 2018 16:12:26 +0000 Message-ID: <20180319161117.17833-44-alexander.levin@microsoft.com> References: <20180319161117.17833-1-alexander.levin@microsoft.com> In-Reply-To: <20180319161117.17833-1-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;DM5PR2101MB1048;7:Tfz+90bT27s+er3xSmagkCPL4EL+FcYy68c1mKLpC2VSoykcWvIk6q4zWVsWZL7A1IqxkNv/cHdA2N25t3VebpLcyzIcj0/27E4615M/FdeiDNRB5X8WnITVVvRuemXbTGexHSn//gNHLtes71xiGAGK3H1byQV0uDEMbxzdMIj1yFQD4HT2o6dQ0+Y+t5HjEv6zy/xbyLEUAc4de+bgTttPxZnlIkMpCEa+st6EAFythRQjPZbpYNV0wHy/Ekhh;20:ZEc7MXjTUvII80hjfYuX8wJg7CZGxWLNGfDuzFO1C/bIbT8JDfwDqgacfpQ7rRfrH3MYcYusySpQJe2I0Q/xzgFYw1/mFcqsvQ/pZl4QlCVTC0wmEUbP2ESb2Ncdnm7nBEnFBl2fa2djvke++NmkGmJG9jJ7KE+Bz/Fr78T2yKo= x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 50e4b348-d2dc-46b0-9ded-08d58db444db x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7193020);SRVR:DM5PR2101MB1048; 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x-microsoft-antispam-message-info: ls4muSuuenhzNAyjgwWux7k/Hcs2tdG1My0ZhAuRJnu3FSM1TYiZQt5ycdLzYAwKicxCJ5XhkilneiWtUTxF2C/2+w5G0PQy3urkpSMRQO0x8sHE+A6mKfxfbcYblmxmPLPVWB8NiXQJgY6uuqFoS19mFAjNhrbBeoEc5rmI2A+vEzuEGzzSRVPUIHVG/YimEpgUFxNvwLbq03CuF7WnFyvQ72LFnC7cUPSo9pLvXmZojNVa28QaRKEffqeUvUIAXmIGrC7AQqNzqqA4egiYCVUo1VYC/Ty3d5rJuAN+Ur4f0eRfRL7f8IEbZQNPZOV3jKwX7nk0WZBmDVEkwLJhPA== 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: 50e4b348-d2dc-46b0-9ded-08d58db444db X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Mar 2018 16:12:26.8070 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB1048 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 d55156fc064d..73049abf4898 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -863,12 +863,16 @@ 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