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Revision 471f0aa7fa64e23766a1473b32d9ec3f0718895a authored by Chang S. Bae on 21 October 2022, 18:58:44 UTC, committed by Dave Hansen on 21 October 2022, 22:22:09 UTC 
x86/fpu: Fix copy_xstate_to_uabi() to copy init states correctly
 
When an extended state component is not present in fpstate, but in init
state, the function copies from init_fpstate via copy_feature().

But, dynamic states are not present in init_fpstate because of all-zeros
init states. Then retrieving them from init_fpstate will explode like this:

 BUG: kernel NULL pointer dereference, address: 0000000000000000
 ...
 RIP: 0010:memcpy_erms+0x6/0x10
  ? __copy_xstate_to_uabi_buf+0x381/0x870
  fpu_copy_guest_fpstate_to_uabi+0x28/0x80
  kvm_arch_vcpu_ioctl+0x14c/0x1460 [kvm]
  ? __this_cpu_preempt_check+0x13/0x20
  ? vmx_vcpu_put+0x2e/0x260 [kvm_intel]
  kvm_vcpu_ioctl+0xea/0x6b0 [kvm]
  ? kvm_vcpu_ioctl+0xea/0x6b0 [kvm]
  ? __fget_light+0xd4/0x130
  __x64_sys_ioctl+0xe3/0x910
  ? debug_smp_processor_id+0x17/0x20
  ? fpregs_assert_state_consistent+0x27/0x50
  do_syscall_64+0x3f/0x90
  entry_SYSCALL_64_after_hwframe+0x63/0xcd

Adjust the 'mask' to zero out the userspace buffer for the features that
are not available both from fpstate and from init_fpstate.

The dynamic features depend on the compacted XSAVE format. Ensure it is
enabled before reading XCOMP_BV in init_fpstate.

Fixes: 2308ee57d93d ("x86/fpu/amx: Enable the AMX feature in 64-bit mode")
Reported-by: Yuan Yao <yuan.yao@intel.com>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Tested-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/lkml/BYAPR11MB3717EDEF2351C958F2C86EED95259@BYAPR11MB3717.namprd11.prod.outlook.com/
Link: https://lkml.kernel.org/r/20221021185844.13472-1-chang.seok.bae@intel.com
1 parent b329f5d
Raw File
refs.h 
#ifndef IOU_REQ_REF_H
#define IOU_REQ_REF_H

#include <linux/atomic.h>
#include <linux/io_uring_types.h>

/*
 * Shamelessly stolen from the mm implementation of page reference checking,
 * see commit f958d7b528b1 for details.
 */
#define req_ref_zero_or_close_to_overflow(req)	\
	((unsigned int) atomic_read(&(req->refs)) + 127u <= 127u)

static inline bool req_ref_inc_not_zero(struct io_kiocb *req)
{
	WARN_ON_ONCE(!(req->flags & REQ_F_REFCOUNT));
	return atomic_inc_not_zero(&req->refs);
}

static inline bool req_ref_put_and_test(struct io_kiocb *req)
{
	if (likely(!(req->flags & REQ_F_REFCOUNT)))
		return true;

	WARN_ON_ONCE(req_ref_zero_or_close_to_overflow(req));
	return atomic_dec_and_test(&req->refs);
}

static inline void req_ref_get(struct io_kiocb *req)
{
	WARN_ON_ONCE(!(req->flags & REQ_F_REFCOUNT));
	WARN_ON_ONCE(req_ref_zero_or_close_to_overflow(req));
	atomic_inc(&req->refs);
}

static inline void __io_req_set_refcount(struct io_kiocb *req, int nr)
{
	if (!(req->flags & REQ_F_REFCOUNT)) {
		req->flags |= REQ_F_REFCOUNT;
		atomic_set(&req->refs, nr);
	}
}

static inline void io_req_set_refcount(struct io_kiocb *req)
{
	__io_req_set_refcount(req, 1);
}
#endif
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