From 1f41390c3d1e659d8a01a92a068e572013d4b35c Mon Sep 17 00:00:00 2001 From: Douglas Bagnall Date: Sun, 19 Jan 2020 15:08:58 +1300 Subject: [PATCH] nmblib: avoid undefined behaviour in handle_name_ptrs() If *offset is length - 1, we would read ubuf[(*offset)+1] as the lower bits of the new *offset. This value is undefined, but because it is checked against the valid range, there is no way to read future beyond that one byte. Credit to oss-fuzz. BUG: https://bugzilla.samba.org/show_bug.cgi?id=14242 OSS-FUZZ: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=20193 Signed-off-by: Douglas Bagnall --- source3/libsmb/nmblib.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/source3/libsmb/nmblib.c b/source3/libsmb/nmblib.c index 84cbb054b8e..c05fac2bba9 100644 --- a/source3/libsmb/nmblib.c +++ b/source3/libsmb/nmblib.c @@ -160,6 +160,9 @@ static bool handle_name_ptrs(unsigned char *ubuf,int *offset,int length, if (!*got_pointer) (*ret) += 2; (*got_pointer)=True; + if (*offset > length - 2) { + return False; + } (*offset) = ((ubuf[*offset] & ~0xC0)<<8) | ubuf[(*offset)+1]; if (loop_count++ == 10 || (*offset) < 0 || (*offset)>(length-2)) { -- 2.20.1