commit 922334f6fb875169d64f9c33cba62d0dafc9faa2
author Mike McTernan <mikemcternan@google.com> Fri Jul 22 11:44:33 2022 +0100
committer Android Build Coastguard Worker <android-build-coastguard-worker@google.com> Wed Sep 14 17:52:04 2022 +0000
tree a601ae0aecc78615e5ffc950b6ae5b05d5cc3173
parent b00f23a828c59eec42e97a9f90f80ad98075c950

Fix integer wrap sanitisation.

Test: make check
Test: afl-clang with new corpus data
Bug: 239630493
Change-Id: I232155e7f7a54271a6a3e3a7cd91ed6bbabc051f
Merged-In: I232155e7f7a54271a6a3e3a7cd91ed6bbabc051f
(cherry picked from commit 05dec6d1827dc7016cad11c4ddfe8f965bceddb7)
(cherry picked from commit 8ef746c547044b107da65c054daedf33075027b6)
Merged-In: I232155e7f7a54271a6a3e3a7cd91ed6bbabc051f

libfdt/fdt.c

diff --git a/libfdt/fdt.c b/libfdt/fdt.c
index 82521b7..17ac7d6 100644
--- a/libfdt/fdt.c
+++ b/libfdt/fdt.c
@@ -180,12 +180,20 @@
 		break;
 
 	case FDT_PROP:
-		lenp = fdt_offset_ptr(fdt, offset, sizeof(*lenp));
+		lenp = fdt_offset_ptr(fdt, offset, sizeof(struct fdt_property) - FDT_TAGSIZE);
 		if (!can_assume(VALID_DTB) && !lenp)
 			return FDT_END; /* premature end */
-		/* skip-name offset, length and value */
-		offset += sizeof(struct fdt_property) - FDT_TAGSIZE
-			+ fdt32_to_cpu(*lenp);
+
+		/* skip name offset, length */
+		offset += sizeof(struct fdt_property) - FDT_TAGSIZE;
+
+		if (!can_assume(VALID_DTB)
+		    && !fdt_offset_ptr(fdt, offset, fdt32_to_cpu(*lenp)))
+			return FDT_END; /* premature end */
+
+		/* skip value */
+		offset += fdt32_to_cpu(*lenp);
+
 		if (!can_assume(LATEST) &&
 		    fdt_version(fdt) < 0x10 && fdt32_to_cpu(*lenp) >= 8 &&
 		    ((offset - fdt32_to_cpu(*lenp)) % 8) != 0)
@@ -201,7 +209,8 @@
 		return FDT_END;
 	}
 
-	if (!fdt_offset_ptr(fdt, startoffset, offset - startoffset))
+	if (!can_assume(VALID_DTB) && (offset <= startoffset
+	    || !fdt_offset_ptr(fdt, startoffset, offset - startoffset)))
 		return FDT_END; /* premature end */
 
 	*nextoffset = FDT_TAGALIGN(offset);