[PATCH] drm/amdkfd: reject alloc_memory_of_gpu with wrapping va_addr/mmap_offset

[Hari Mishal <harimishal1@gmail.com>]

kfd_ioctl_alloc_memory_of_gpu() computes the SVM overlap-check range as
[va_addr, va_addr + size - 1] (and likewise for mmap_offset) and passes
it to interval_tree_iter_first() with no check that the addition can
overflow u64. With va_addr near U64_MAX, the end wraps below start,
interval_tree_iter_first() sees an inverted range and returns NULL, and
the overlap check is silently skipped. /dev/kfd is unprivileged, and
va_addr/size/mmap_offset are plain fields in the ioctl argument struct
supplied directly by the calling process, so this is reachable by any
local user with a single crafted ioctl call.

Reject the ioctl when either va_addr+size or mmap_offset+size overflows,
using check_add_overflow().

Signed-off-by: Hari Mishal <harimishal1@gmail.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
index 309510e23315..12954d65503c 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
@@ -1089,10 +1089,15 @@ static int kfd_ioctl_alloc_memory_of_gpu(struct file *filep,
 	long err;
 	uint64_t offset = args->mmap_offset;
 	uint32_t flags = args->flags;
+	u64 end;
 
 	if (args->size == 0)
 		return -EINVAL;
 
+	if (check_add_overflow(args->va_addr, args->size, &end) ||
+	    check_add_overflow(args->mmap_offset, args->size, &end))
+		return -EINVAL;
+
 	if (p->context_id != KFD_CONTEXT_ID_PRIMARY && (flags & KFD_IOC_ALLOC_MEM_FLAGS_USERPTR)) {
 		pr_debug("USERPTR is not supported on non-primary kfd_process\n");
 
-- 
2.43.0