From: David Gibson <da...@gibson.dropbear.id.au>
Using pointer arithmetic to generate a pointer outside a known object is,
technically, undefined behaviour in C. Unfortunately, we were using that
in fdt_offset_ptr() to detect overflows.
To fix this we need to do our bounds / overflow checking on the offsets
before constructing pointers from them.
Reported-by: David Binderman <dcb...@hotmail.com>
Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
Signed-off-by: Simon Glass <s...@chromium.org>
---
lib/libfdt/fdt.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/lib/libfdt/fdt.c b/lib/libfdt/fdt.c
index 96017a1..2055734 100644
--- a/lib/libfdt/fdt.c
+++ b/lib/libfdt/fdt.c
@@ -35,18 +35,19 @@ int fdt_check_header(const void *fdt)
const void *fdt_offset_ptr(const void *fdt, int offset, unsigned int len)
{
- const char *p;
+ unsigned absoffset = offset + fdt_off_dt_struct(fdt);
+
+ if ((absoffset < offset)
+ || ((absoffset + len) < absoffset)
+ || (absoffset + len) > fdt_totalsize(fdt))
+ return NULL;
if (fdt_version(fdt) >= 0x11)
if (((offset + len) < offset)
|| ((offset + len) > fdt_size_dt_struct(fdt)))
return NULL;
- p = _fdt_offset_ptr(fdt, offset);
-
- if (p + len < p)
- return NULL;
- return p;
+ return _fdt_offset_ptr(fdt, offset);
}
uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
--
2.8.0.rc3.226.g39d4020
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