Re: [PATCH AUTOSEL 6.18] perf/core: Fix kernel register info leak via hardware skid

[sashiko-bot@kernel.org]

> From: Dapeng Mi <dapeng1.mi@linux.intel.com>
> 
> [ Upstream commit 166f10836a653dfa280d4335603b52f685b8b1ef ]
> 
> An unprivileged hardware perf event using exclude_kernel=1 can leak kernel
> register data to user space via PERF_SAMPLE_REGS_INTR or PERF_SAMPLE_IP.
> Due to hardware skid, a PMI may trigger after the CPU has already entered
> kernel space (Ring 0), bypassing the perf_allow_kernel() privilege
> barrier.
> 
> This security vulnerability is severely exacerbated by upcoming support
> for SIMD register sampling via XSAVES, which could expose sensitive kernel
> FPU states (such as active cryptographic keys).
> 
> Fix this by ensuring that sampled register data is dropped if the event's
> exclude_kernel attribute is set but the PMI catches the CPU in kernel mode.
> 
> Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Link: https://lore.kernel.org/all/20260529085613.CCAFB1F00893@smtp.kernel.org/
> Link: https://patch.msgid.link/20260616044654.3468742-8-dapeng1.mi@linux.intel.com
> Signed-off-by: Sasha Levin <sashal@kernel.org>

Sashiko has reviewed this patch and found no issues.

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