From: Naman Jain Date: Mon, 6 Apr 2026 09:24:59 +0000 (+0000) Subject: mshv_vtl: Fix vmemmap_shift exceeding MAX_FOLIO_ORDER X-Git-Tag: v7.1-rc1~51^2~4 X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=404cd6bffe17e25e0f94ed2775ffdd6cd10ac3fd;p=thirdparty%2Fkernel%2Flinux.git 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 646b67d57589 ("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: 7bfe3b8ea6e3 ("Drivers: hv: Introduce mshv_vtl driver") Cc: stable@vger.kernel.org Signed-off-by: Naman Jain Reviewed-by: Michael Kelley Signed-off-by: Wei Liu --- diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c index 5856975f32e1..c19400701467 100644 --- a/drivers/hv/mshv_vtl_main.c +++ b/drivers/hv/mshv_vtl_main.c @@ -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 diff --git a/include/uapi/linux/mshv.h b/include/uapi/linux/mshv.h index e0645a34b55b..32ff92b6342b 100644 --- a/include/uapi/linux/mshv.h +++ b/include/uapi/linux/mshv.h @@ -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 {