fdt_num_mem_rsv() can return a negative error value, when the memreserve
block is not properly terminated or is exceeding its advertised size,
This can happen on malformed DTBs, and FDT_RO_PROBE() does not cover this.
Check the return value of fdt_num_mem_rsv() first for an error
condition, and also check if the total size of the memreserve block
would provoke a signed integer overflow.
This fixes issues with malformed DT blobs, where we would end up with
negative offsets into buffers.
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
libfdt/fdt_rw.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/libfdt/fdt_rw.c b/libfdt/fdt_rw.c
index 3621d36..a0f03d0 100644
--- a/libfdt/fdt_rw.c
+++ b/libfdt/fdt_rw.c
@@ -427,8 +427,13 @@ int fdt_open_into(const void *fdt, void *buf, int bufsize)
FDT_RO_PROBE(fdt);
- mem_rsv_size = (fdt_num_mem_rsv(fdt)+1)
- * sizeof(struct fdt_reserve_entry);
+ mem_rsv_size = fdt_num_mem_rsv(fdt);
+ if (mem_rsv_size < 0)
+ return mem_rsv_size;
+
+ mem_rsv_size = (mem_rsv_size + 1) * sizeof(struct fdt_reserve_entry);
+ if (!can_assume(VALID_DTB) && mem_rsv_size < 0)
+ return -FDT_ERR_NOSPACE;
if (can_assume(LATEST) || fdt_version(fdt) >= 17) {
struct_size = fdt_size_dt_struct(fdt);
@@ -490,8 +495,14 @@ int fdt_pack(void *fdt)
FDT_RW_PROBE(fdt);
- mem_rsv_size = (fdt_num_mem_rsv(fdt)+1)
- * sizeof(struct fdt_reserve_entry);
+ mem_rsv_size = fdt_num_mem_rsv(fdt);
+ if (mem_rsv_size < 0)
+ return mem_rsv_size;
+
+ mem_rsv_size = (mem_rsv_size + 1) * sizeof(struct fdt_reserve_entry);
+ if (!can_assume(VALID_DTB) && mem_rsv_size < 0)
+ return -FDT_ERR_NOSPACE;
+
fdt_packblocks_(fdt, fdt, mem_rsv_size, fdt_size_dt_struct(fdt),
fdt_size_dt_strings(fdt));
fdt_set_totalsize(fdt, fdt_data_size_(fdt));
--
2.17.5
