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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Sep 2025 15:08:36.2101 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: eb060965-2d22-4695-d8c6-08ddfd0e9126 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: DU6PEPF00009527.eurprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: GV2PR08MB11444 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250926_080843_744717_513D8B3D X-CRM114-Status: GOOD ( 18.09 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On Thu, Sep 25, 2025 at 08:40:56PM +0000, Edgecombe, Rick P wrote: > On Sun, 2025-09-21 at 14:21 +0100, Mark Brown wrote: > > During the discussion of the clone3() support for shadow stacks concerns > > were raised from the glibc side that since it is not possible to reuse > > the allocated shadow stack[1]. This means that the benefit of being able > > ... > > > Security-wise, it seems reasonable that if you are leaving a shadow stack, that > you could leave a token behind. But for the userspace scheme to back up the SSP > by doing a longjmp() or similar I have some doubts. IIRC there were some cross > stack edge cases that we never figured out how to handle. > > As far as re-using allocated shadow stacks, there is always the option to enable > WRSS (or similar) to write the shadow stack as well as longjmp at will. > > I think we should see a fuller solution from the glibc side before adding new > kernel features like this. (apologies if I missed it). What do you mean by "a fuller solution from the glibc side"? A solution for re-using shadow stacks? Right now Glibc cannot do anything about shadow stacks for new threads because clone3 interface doesn't allow it. Thanks, Yury