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Wysocki" , Pavel Machek , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "x86@kernel.org" , "H . Peter Anvin" , Chen Yu , Pawan Gupta , Catalin Marinas , Linux Memory Management , "Rafael J . Wysocki" , Ingo Molnar , "linux-pm@vger.kernel.org" , Linux Kernel , "stable@vger.kernel.org" Subject: Re: [PATCH] x86/pm: Fix false positive kmemleak report in msr_build_context(). Thread-Topic: [PATCH] x86/pm: Fix false positive kmemleak report in msr_build_context(). 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charset="us-ascii" Content-ID: <5EBCB49079CC674890FFC0406646BE57@eurprd06.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: tuxera.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: AS8PR06MB7239.eurprd06.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: ba1b3b2a-4e8d-4de4-552f-08dc443dcf80 X-MS-Exchange-CrossTenant-originalarrivaltime: 14 Mar 2024 15:45:44.4159 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: e7fd1de3-6111-47e9-bf5d-4c1ca2ed0b84 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 1yQNlXEZ6PYOUfM3UEAuC637C2laLH83UWxxJB373skPx3XSPnMbZpEkHpvFExSxudjcMVYfEkRq4CtxT2CSEw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS8PR06MB7766 X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: BDED980028 X-Stat-Signature: 6efs4ceaq3n8wa51bgc7z4fi6jcd9jk3 X-HE-Tag: 1710431147-413796 X-HE-Meta: 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 C/9m0zDz iWRjfqpF2xplgeydYIl/LOxXQBw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Dave, > On 14 Mar 2024, at 15:05, Dave Hansen wrote: >=20 > On 3/14/24 07:26, Anton Altaparmakov wrote: >> /* image of the saved processor state */ >> struct saved_context { >> - /* >> - * On x86_32, all segment registers except gs are saved at kernel >> - * entry in pt_regs. >> - */ >> - u16 gs; >> unsigned long cr0, cr2, cr3, cr4; >> u64 misc_enable; >> struct saved_msrs saved_msrs; >> @@ -27,6 +22,11 @@ struct saved_context { >> unsigned long tr; >> unsigned long safety; >> unsigned long return_address; >> + /* >> + * On x86_32, all segment registers except gs are saved at kernel >> + * entry in pt_regs. >> + */ >> + u16 gs; >> bool misc_enable_saved; >> } __attribute__((packed)); >=20 > Isn't this just kinda poking at the symptoms? This seems to be > basically the exact same bug as b0b592cf08, just with a different source > of unaligned structure members. Yes, that is exactly the same bug. That's how we figured out the solution = in fact - it is totally the same problem with another struct member... > There's nothing to keep folks from reintroducing these kinds of issues > and evidently no way to detect when they happen without lengthy reproduce= rs. Correct. But short of adding asserts / documentation that pointers must be= aligned or kmemleak won't work or fixing kmemleak (which I expect is not t= ractical as it would become a lot slower if nothing else) not sure what els= e can be done. Given I cannot see any alternative to fixing the kmemleak failures I think = it is worth applying this fix. Unless you have better ideas how to fix this issue? What I can say is that we run a lot of tests with our CI and applying this = fix we do not see any kmemleak issues any more whilst without it we see hun= dreds of the above - from a single, simple test run consisting of 416 indiv= idual test cases on kernel 5.10 x86 with kmemleak enabled we got 20 failure= s due to this which is quite a lot. With this fix applied we get zero kmem= leak related failures. Best regards, Anton --=20 Anton Altaparmakov (replace at with @) Lead in File System Development, Tuxera Inc., http://www.tuxera.com/