Revision - 471f0aa - x86/fpu: Fix copy_xstate_to_uabi() to copy init states correctly

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

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xattr.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/namei.h>
#include <linux/io_uring.h>
#include <linux/xattr.h>

#include <uapi/linux/io_uring.h>

#include "../fs/internal.h"

#include "io_uring.h"
#include "xattr.h"

struct io_xattr {
	struct file			*file;
	struct xattr_ctx		ctx;
	struct filename			*filename;
};

void io_xattr_cleanup(struct io_kiocb *req)
{
	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);

	if (ix->filename)
		putname(ix->filename);

	kfree(ix->ctx.kname);
	kvfree(ix->ctx.kvalue);
}

static void io_xattr_finish(struct io_kiocb *req, int ret)
{
	req->flags &= ~REQ_F_NEED_CLEANUP;

	io_xattr_cleanup(req);
	io_req_set_res(req, ret, 0);
}

static int __io_getxattr_prep(struct io_kiocb *req,
			      const struct io_uring_sqe *sqe)
{
	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
	const char __user *name;
	int ret;

	if (unlikely(req->flags & REQ_F_FIXED_FILE))
		return -EBADF;

	ix->filename = NULL;
	ix->ctx.kvalue = NULL;
	name = u64_to_user_ptr(READ_ONCE(sqe->addr));
	ix->ctx.cvalue = u64_to_user_ptr(READ_ONCE(sqe->addr2));
	ix->ctx.size = READ_ONCE(sqe->len);
	ix->ctx.flags = READ_ONCE(sqe->xattr_flags);

	if (ix->ctx.flags)
		return -EINVAL;

	ix->ctx.kname = kmalloc(sizeof(*ix->ctx.kname), GFP_KERNEL);
	if (!ix->ctx.kname)
		return -ENOMEM;

	ret = strncpy_from_user(ix->ctx.kname->name, name,
				sizeof(ix->ctx.kname->name));
	if (!ret || ret == sizeof(ix->ctx.kname->name))
		ret = -ERANGE;
	if (ret < 0) {
		kfree(ix->ctx.kname);
		return ret;
	}

	req->flags |= REQ_F_NEED_CLEANUP;
	return 0;
}

int io_fgetxattr_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	return __io_getxattr_prep(req, sqe);
}

int io_getxattr_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
	const char __user *path;
	int ret;

	ret = __io_getxattr_prep(req, sqe);
	if (ret)
		return ret;

	path = u64_to_user_ptr(READ_ONCE(sqe->addr3));

	ix->filename = getname_flags(path, LOOKUP_FOLLOW, NULL);
	if (IS_ERR(ix->filename)) {
		ret = PTR_ERR(ix->filename);
		ix->filename = NULL;
	}

	return ret;
}

int io_fgetxattr(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
	int ret;

	if (issue_flags & IO_URING_F_NONBLOCK)
		return -EAGAIN;

	ret = do_getxattr(mnt_user_ns(req->file->f_path.mnt),
			req->file->f_path.dentry,
			&ix->ctx);

	io_xattr_finish(req, ret);
	return IOU_OK;
}

int io_getxattr(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
	unsigned int lookup_flags = LOOKUP_FOLLOW;
	struct path path;
	int ret;

	if (issue_flags & IO_URING_F_NONBLOCK)
		return -EAGAIN;

retry:
	ret = filename_lookup(AT_FDCWD, ix->filename, lookup_flags, &path, NULL);
	if (!ret) {
		ret = do_getxattr(mnt_user_ns(path.mnt),
				path.dentry,
				&ix->ctx);

		path_put(&path);
		if (retry_estale(ret, lookup_flags)) {
			lookup_flags |= LOOKUP_REVAL;
			goto retry;
		}
	}

	io_xattr_finish(req, ret);
	return IOU_OK;
}

static int __io_setxattr_prep(struct io_kiocb *req,
			const struct io_uring_sqe *sqe)
{
	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
	const char __user *name;
	int ret;

	if (unlikely(req->flags & REQ_F_FIXED_FILE))
		return -EBADF;

	ix->filename = NULL;
	name = u64_to_user_ptr(READ_ONCE(sqe->addr));
	ix->ctx.cvalue = u64_to_user_ptr(READ_ONCE(sqe->addr2));
	ix->ctx.kvalue = NULL;
	ix->ctx.size = READ_ONCE(sqe->len);
	ix->ctx.flags = READ_ONCE(sqe->xattr_flags);

	ix->ctx.kname = kmalloc(sizeof(*ix->ctx.kname), GFP_KERNEL);
	if (!ix->ctx.kname)
		return -ENOMEM;

	ret = setxattr_copy(name, &ix->ctx);
	if (ret) {
		kfree(ix->ctx.kname);
		return ret;
	}

	req->flags |= REQ_F_NEED_CLEANUP;
	return 0;
}

int io_setxattr_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
	const char __user *path;
	int ret;

	ret = __io_setxattr_prep(req, sqe);
	if (ret)
		return ret;

	path = u64_to_user_ptr(READ_ONCE(sqe->addr3));

	ix->filename = getname_flags(path, LOOKUP_FOLLOW, NULL);
	if (IS_ERR(ix->filename)) {
		ret = PTR_ERR(ix->filename);
		ix->filename = NULL;
	}

	return ret;
}

int io_fsetxattr_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	return __io_setxattr_prep(req, sqe);
}

static int __io_setxattr(struct io_kiocb *req, unsigned int issue_flags,
			const struct path *path)
{
	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
	int ret;

	ret = mnt_want_write(path->mnt);
	if (!ret) {
		ret = do_setxattr(mnt_user_ns(path->mnt), path->dentry, &ix->ctx);
		mnt_drop_write(path->mnt);
	}

	return ret;
}

int io_fsetxattr(struct io_kiocb *req, unsigned int issue_flags)
{
	int ret;

	if (issue_flags & IO_URING_F_NONBLOCK)
		return -EAGAIN;

	ret = __io_setxattr(req, issue_flags, &req->file->f_path);
	io_xattr_finish(req, ret);
	return IOU_OK;
}

int io_setxattr(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
	unsigned int lookup_flags = LOOKUP_FOLLOW;
	struct path path;
	int ret;

	if (issue_flags & IO_URING_F_NONBLOCK)
		return -EAGAIN;

retry:
	ret = filename_lookup(AT_FDCWD, ix->filename, lookup_flags, &path, NULL);
	if (!ret) {
		ret = __io_setxattr(req, issue_flags, &path);
		path_put(&path);
		if (retry_estale(ret, lookup_flags)) {
			lookup_flags |= LOOKUP_REVAL;
			goto retry;
		}
	}

	io_xattr_finish(req, ret);
	return IOU_OK;
}

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