binder: fix incorrect calculation for num_valid

For BINDER_TYPE_PTR and BINDER_TYPE_FDA transactions, the num_valid local was calculated incorrectly causing the range check in binder_validate_ptr() to miss out-of-bounds offsets. Fixes: bde4a19 ("binder: use userspace pointer as base of buffer space") Signed-off-by: Todd Kjos <[email protected]> Cc: stable <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]>
berg · Dec 14, 2019 · 1698174 · 1698174
1 parent 3e42fe5
commit 1698174
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
@@ -3310,7 +3310,7 @@ static void binder_transaction(struct binder_proc *proc,
 			binder_size_t parent_offset;
 			struct binder_fd_array_object *fda =
 				to_binder_fd_array_object(hdr);
-			size_t num_valid = (buffer_offset - off_start_offset) *
+			size_t num_valid = (buffer_offset - off_start_offset) /
 						sizeof(binder_size_t);
 			struct binder_buffer_object *parent =
 				binder_validate_ptr(target_proc, t->buffer,
@@ -3384,7 +3384,7 @@ static void binder_transaction(struct binder_proc *proc,
 				t->buffer->user_data + sg_buf_offset;
 			sg_buf_offset += ALIGN(bp->length, sizeof(u64));
 
-			num_valid = (buffer_offset - off_start_offset) *
+			num_valid = (buffer_offset - off_start_offset) /
 					sizeof(binder_size_t);
 			ret = binder_fixup_parent(t, thread, bp,
 						  off_start_offset,