From aa16b2bc0f02709919e2435f531406531e5bcc69 Mon Sep 17 00:00:00 2001 From: Zack McKevitt Date: Thu, 30 Apr 2026 12:39:01 -0700 Subject: [PATCH] accel/qaic: Add overflow check to remap_pfn_range during mmap The call to remap_pfn_range in qaic_gem_object_mmap is susceptible to (re)mapping beyond the VMA if the BO is too large. This can cause use after free issues when munmap() unmaps only the VMA region and not the additional mappings. To prevent this, check the remaining size of the VMA before remapping and truncate the remapped length if sg->length is too large. Reported-by: Lukas Maar Fixes: ff13be830333 ("accel/qaic: Add datapath") Reviewed-by: Karol Wachowski Signed-off-by: Zack McKevitt Reviewed-by: Jeff Hugo [jhugo: fix braces from checkpatch --strict] Signed-off-by: Jeff Hugo Link: https://patch.msgid.link/20260430193858.1178641-1-zachary.mckevitt@oss.qualcomm.com --- drivers/accel/qaic/qaic_data.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/drivers/accel/qaic/qaic_data.c b/drivers/accel/qaic/qaic_data.c index 95300c2f7d8a..1e4c579d2725 100644 --- a/drivers/accel/qaic/qaic_data.c +++ b/drivers/accel/qaic/qaic_data.c @@ -606,8 +606,11 @@ static const struct vm_operations_struct drm_vm_ops = { static int qaic_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma) { struct qaic_bo *bo = to_qaic_bo(obj); + unsigned long remap_start; unsigned long offset = 0; + unsigned long remap_end; struct scatterlist *sg; + unsigned long length; int ret = 0; if (drm_gem_is_imported(obj)) @@ -615,11 +618,27 @@ static int qaic_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struc for (sg = bo->sgt->sgl; sg; sg = sg_next(sg)) { if (sg_page(sg)) { + /* if sg is too large for the VMA, so truncate it to fit */ + if (check_add_overflow(vma->vm_start, offset, &remap_start)) + return -EINVAL; + if (check_add_overflow(remap_start, sg->length, &remap_end)) + return -EINVAL; + + if (remap_end > vma->vm_end) { + if (check_sub_overflow(vma->vm_end, remap_start, &length)) + return -EINVAL; + } else { + length = sg->length; + } + + if (length == 0) + goto out; + ret = remap_pfn_range(vma, vma->vm_start + offset, page_to_pfn(sg_page(sg)), - sg->length, vma->vm_page_prot); + length, vma->vm_page_prot); if (ret) goto out; - offset += sg->length; + offset += length; } }