From: Tadeusz Struk <tadeusz.struk-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
To: David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>
Cc: devicetree-compiler-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
tadeusz.struk-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org
Subject: [PATCH 1/2] libfdt: prevent integer overflow in fdt_next_tag
Date: Thu, 29 Sep 2022 16:55:35 -0700 [thread overview]
Message-ID: <20220929235536.618370-1-tadeusz.struk@linaro.org> (raw)
Since fdt_next_tag() in a public API function all input parameters,
including the fdt blob should not be trusted. It is possible to forge
a blob with invalid property length that will cause integer overflow
during offset calculation. To prevent that validate the property length
read from the blob before doing calculations.
Signed-off-by: Tadeusz Struk <tadeusz.struk-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
libfdt/fdt.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/libfdt/fdt.c b/libfdt/fdt.c
index 90a39e8..c3e112a 100644
--- a/libfdt/fdt.c
+++ b/libfdt/fdt.c
@@ -186,11 +186,17 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
case FDT_PROP:
lenp = fdt_offset_ptr(fdt, offset, sizeof(*lenp));
- if (!can_assume(VALID_DTB) && !lenp)
+ if (!can_assume(VALID_DTB) &&
+ (!lenp || (INT_MAX <= fdt32_to_cpu(*lenp))))
return FDT_END; /* premature end */
+
/* skip-name offset, length and value */
offset += sizeof(struct fdt_property) - FDT_TAGSIZE
+ fdt32_to_cpu(*lenp);
+
+ if (offset < 0)
+ return FDT_END; /* premature end */
+
if (!can_assume(LATEST) &&
fdt_version(fdt) < 0x10 && fdt32_to_cpu(*lenp) >= 8 &&
((offset - fdt32_to_cpu(*lenp)) % 8) != 0)
--
2.37.3
next reply other threads:[~2022-09-29 23:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-29 23:55 Tadeusz Struk [this message]
[not found] ` <20220929235536.618370-1-tadeusz.struk-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2022-09-29 23:55 ` [PATCH 2/2] libfdt: tests: add get_next_tag_invalid_prop_len Tadeusz Struk
2022-09-30 13:18 ` [PATCH 1/2] libfdt: prevent integer overflow in fdt_next_tag Rob Herring
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