Re: [PATCH v9 14/26] x86/arch_prctl: Create ARCH_SET_STATE_ENABLE/ARCH_GET_STATE_ENABLE
From: Bae, Chang Seok <hidden>
Date: 2021-08-10 00:57:39
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
On Aug 9, 2021, at 16:42, Macieira, Thiago [off-list ref] wrote:
This means the corruption can get worse since the rollback code can undo or partially undo the progression of the other ARCH_SET_STATE_ENABLE.
Maybe something like this can help here to ensure a valid rollback.
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 96056f49bcff..3468bc0ee654 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c@@ -1353,6 +1353,8 @@ int alloc_xstate_buffer(struct fpu *fpu, u64 mask) return 0;
} +static DEFINE_SPINLOCK(set_xstate_perm_lock); + /** * set_process_xstate_perm - Set a per-process permission to use dynamic * user xstates.
@@ -1383,6 +1385,8 @@ long set_process_xstate_perm(struct task_struct *tsk, u64 state_perm) if (!req_dynstate_perm) return 0; + spin_lock(&set_xstate_perm_lock); + old_dynstate_perm = tsk->thread.fpu.dynamic_state_perm; for_each_thread(tsk, t) {
@@ -1396,6 +1400,8 @@ long set_process_xstate_perm(struct task_struct *tsk, u64 state_perm) pr_err("x86/fpu: ARCH_XSTATE_PERM failed as thread number mismatched.\n"); return -EBUSY; } + + spin_unlock(&set_xstate_perm_lock); return 0;
} Thanks, Chang