Commit 68a4b481 authored Aug 14, 2019 by Daniel Jordan Committed by Xie XiuQi Dec 27, 2019

vfio: remove unnecessary mmap_sem writer acquisition around locked_vm



hulk inclusion
category: feature
bugzilla: 13228
CVE: NA
---------------------------

Now that mmap_sem is no longer required for modifying locked_vm, remove
it in the VFIO code.

[XXX Can be sent separately, along with similar conversions in the other
places mmap_sem was taken for locked_vm.  While at it, could make
similar changes to pinned_vm.]

Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Hongbo Yao <yaohongbo@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Tested-by: Hongbo Yao <yaohongbo@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>

parent 53f4e528

drivers/vfio/vfio_iommu_type1.c

+9 −18

Original line number	Diff line number	Diff line
		@@ -274,7 +274,8 @@ static int vfio_iova_put_vfio_pfn(struct vfio_dma dma, struct vfio_pfn vpfn)
		static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)
		{
		struct mm_struct *mm;
		int ret;
		long locked_vm;
		int ret = 0;

		if (!npage)
		return 0;
		@@ -283,27 +284,17 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)
		if (!mm)
		return -ESRCH; /* process exited */

		ret = down_write_killable(&mm->mmap_sem);
		if (!ret) {
		if (npage > 0) {
		if (!dma->lock_cap) {
		unsigned long limit;

		limit = task_rlimit(dma->task,
		RLIMIT_MEMLOCK) >> PAGE_SHIFT;
		locked_vm = atomic_long_add_return(npage, &mm->locked_vm);

		if (atomic_long_read(&mm->locked_vm) + npage >
		limit)
		if (npage > 0 && !dma->lock_cap) {
		unsigned long limit = task_rlimit(dma->task, RLIMIT_MEMLOCK) >>
		PAGE_SHIFT;
		if (locked_vm > limit) {
		atomic_long_sub(npage, &mm->locked_vm);
		ret = -ENOMEM;
		}
		}

		if (!ret)
		atomic_long_add(npage, &mm->locked_vm);

		up_write(&mm->mmap_sem);
		}

		if (async)
		mmput(mm);