On Fri, Mar 01, 2024 at 03:12:24PM +0000, Lena Wang (王娜) wrote: > From: Lena Wang <lena.wang@xxxxxxxxxxxx> > > UBSAN load reports an exception of BRK#5515 SHIFT_ISSUE:Bitwise shifts > that are out of bounds for their data type. > > vmlinux get_bitmap(b=75) + 712 > <net/netfilter/nf_conntrack_h323_asn1.c:0> > vmlinux decode_seq(bs=0xFFFFFFD008037000, f=0xFFFFFFD008037018, > level=134443100) + 1956 > <net/netfilter/nf_conntrack_h323_asn1.c:592> > vmlinux decode_choice(base=0xFFFFFFD0080370F0, level=23843636) + 1216 > <net/netfilter/nf_conntrack_h323_asn1.c:814> > vmlinux decode_seq(f=0xFFFFFFD0080371A8, level=134443500) + 812 > <net/netfilter/nf_conntrack_h323_asn1.c:576> > vmlinux decode_choice(base=0xFFFFFFD008037280, level=0) + 1216 > <net/netfilter/nf_conntrack_h323_asn1.c:814> > vmlinux DecodeRasMessage() + 304 > <net/netfilter/nf_conntrack_h323_asn1.c:833> > vmlinux ras_help() + 684 > <net/netfilter/nf_conntrack_h323_main.c:1728> > vmlinux nf_confirm() + 188 > <net/netfilter/nf_conntrack_proto.c:137> > > Due to abnormal data in skb->data, the extension bitmap length > exceeds 32 when decoding ras message. Then get_bitmap uses the > length to make a shift operation. It will change into negative > after several loop. > > UBSAN load can detect a negative shift as an undefined behaviour > and reports an exception. > > So we should add the protection to avoid the length exceeding 32. > If it exceeds it will return out of range error and stop decoding > ras message. > > Signed-off-by: Lena Wang <lena.wang@xxxxxxxxxxxx> > --- > v2: > - add length protecton for another get_bitmap call. > - update commit message to trim stacktrace. > --- > --- > net/netfilter/nf_conntrack_h323_asn1.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/net/netfilter/nf_conntrack_h323_asn1.c > b/net/netfilter/nf_conntrack_h323_asn1.c > index e697a824b001..540d97715bd2 100644 > --- a/net/netfilter/nf_conntrack_h323_asn1.c > +++ b/net/netfilter/nf_conntrack_h323_asn1.c > @@ -533,6 +533,8 @@ static int decode_seq(struct bitstr *bs, const > struct field_t *f, > /* Get fields bitmap */ > if (nf_h323_error_boundary(bs, 0, f->sz)) > return H323_ERROR_BOUND; > + if (f->sz > 32) > + return H323_ERROR_RANGE; Could you possibly place this in get_bitmap()? IIRC these are the only two calls to this function. Thanks. > bmp = get_bitmap(bs, f->sz); > if (base) > *(unsigned int *)base = bmp; > @@ -589,6 +591,8 @@ static int decode_seq(struct bitstr *bs, const > struct field_t *f, > bmp2_len = get_bits(bs, 7) + 1; > if (nf_h323_error_boundary(bs, 0, bmp2_len)) > return H323_ERROR_BOUND; > + if (bmp2_len > 32) > + return H323_ERROR_RANGE; > bmp2 = get_bitmap(bs, bmp2_len); > bmp |= bmp2 >> f->sz; > if (base) > -- > 2.18.0
