Commit 404cd6bf authored by Naman Jain's avatar Naman Jain Committed by Wei Liu
Browse files

mshv_vtl: Fix vmemmap_shift exceeding MAX_FOLIO_ORDER 



When registering VTL0 memory via MSHV_ADD_VTL0_MEMORY, the kernel
computes pgmap->vmemmap_shift as the number of trailing zeros in the
OR of start_pfn and last_pfn, intending to use the largest compound
page order both endpoints are aligned to.

However, this value is not clamped to MAX_FOLIO_ORDER, so a
sufficiently aligned range (e.g. physical range
[0x800000000000, 0x800080000000), corresponding to start_pfn=0x800000000
with 35 trailing zeros) can produce a shift larger than what
memremap_pages() accepts, triggering a WARN and returning -EINVAL:

  WARNING: ... memremap_pages+0x512/0x650
  requested folio size unsupported

The MAX_FOLIO_ORDER check was added by
commit 646b67d5 ("mm/memremap: reject unreasonable folio/compound
page sizes in memremap_pages()").

Fix this by clamping vmemmap_shift to MAX_FOLIO_ORDER so we always
request the largest order the kernel supports, in those cases, rather
than an out-of-range value.

Also fix the error path to propagate the actual error code from
devm_memremap_pages() instead of hard-coding -EFAULT, which was
masking the real -EINVAL return.

Fixes: 7bfe3b8e ("Drivers: hv: Introduce mshv_vtl driver")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarNaman Jain <namjain@linux.microsoft.com>
Reviewed-by: default avatarMichael Kelley <mhklinux@outlook.com>
Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
parent ca5ee0e9

drivers/hv/mshv_vtl_main.c

+9 −3
Original line number Diff line number Diff line
@@ -386,7 +386,6 @@ static int mshv_vtl_ioctl_add_vtl0_mem(struct mshv_vtl *vtl, void __user *arg) 


	if (copy_from_user(&vtl0_mem, arg, sizeof(vtl0_mem)))

		return -EFAULT;

	/* vtl0_mem.last_pfn is excluded in the pagemap range for VTL0 as per design */

	if (vtl0_mem.last_pfn <= vtl0_mem.start_pfn) {

		dev_err(vtl->module_dev, "range start pfn (%llx) > end pfn (%llx)\n",

			vtl0_mem.start_pfn, vtl0_mem.last_pfn);
@@ -397,6 +396,10 @@ static int mshv_vtl_ioctl_add_vtl0_mem(struct mshv_vtl *vtl, void __user *arg) 
	if (!pgmap)

		return -ENOMEM;



	/*

	 * vtl0_mem.last_pfn is excluded in the pagemap range for VTL0 as per design.

	 * last_pfn is not reserved or wasted, and reflects 'start_pfn + size' of pagemap range.

	 */

	pgmap->ranges[0].start = PFN_PHYS(vtl0_mem.start_pfn);

	pgmap->ranges[0].end = PFN_PHYS(vtl0_mem.last_pfn) - 1;

	pgmap->nr_range = 1;
@@ -405,8 +408,11 @@ static int mshv_vtl_ioctl_add_vtl0_mem(struct mshv_vtl *vtl, void __user *arg) 
	/*

	 * Determine the highest page order that can be used for the given memory range.

	 * This works best when the range is aligned; i.e. both the start and the length.

	 * Clamp to MAX_FOLIO_ORDER to avoid a WARN in memremap_pages() when the range

	 * alignment exceeds the maximum supported folio order for this kernel config.

	 */

	pgmap->vmemmap_shift = count_trailing_zeros(vtl0_mem.start_pfn | vtl0_mem.last_pfn);

	pgmap->vmemmap_shift = min(count_trailing_zeros(vtl0_mem.start_pfn | vtl0_mem.last_pfn),

				   MAX_FOLIO_ORDER);

	dev_dbg(vtl->module_dev,

		"Add VTL0 memory: start: 0x%llx, end_pfn: 0x%llx, page order: %lu\n",

		vtl0_mem.start_pfn, vtl0_mem.last_pfn, pgmap->vmemmap_shift);
@@ -415,7 +421,7 @@ static int mshv_vtl_ioctl_add_vtl0_mem(struct mshv_vtl *vtl, void __user *arg) 
	if (IS_ERR(addr)) {

		dev_err(vtl->module_dev, "devm_memremap_pages error: %ld\n", PTR_ERR(addr));

		kfree(pgmap);

		return -EFAULT;

		return PTR_ERR(addr);

	}



	/* Don't free pgmap, since it has to stick around until the memory

include/uapi/linux/mshv.h

+1 −1
Original line number Diff line number Diff line
@@ -357,7 +357,7 @@ struct mshv_vtl_sint_post_msg { 


struct mshv_vtl_ram_disposition {

	__u64 start_pfn;

	__u64 last_pfn;

	__u64 last_pfn; /* last_pfn is excluded from the range [start_pfn, last_pfn) */

};



struct mshv_vtl_set_poll_file {