On Fri, May 01, 2020 at 11:42:28AM +0800, Wang YanQing wrote:
> On Fri, May 01, 2020 at 11:19:50AM +0800, Wang YanQing wrote:
> > commit 50fe7ebb6475711c15b3397467e6424e20026d94 upstream.
> >
> > The current JIT clobbers the destination register for BPF_JSET BPF_X
> > and BPF_K by using "and" and "or" instructions. This is fine when the
> > destination register is a temporary loaded from a register stored on
> > the stack but not otherwise.
> >
> > This patch fixes the problem (for both BPF_K and BPF_X) by always loading
> > the destination register into temporaries since BPF_JSET should not
> > modify the destination register.
> >
> > This bug may not be currently triggerable as BPF_REG_AX is the only
> > register not stored on the stack and the verifier uses it in a limited
> > way.
> >
> > Fixes: 03f5781be2c7b ("bpf, x86_32: add eBPF JIT compiler for ia32")
> > Signed-off-by: Xi Wang <xi.wang@xxxxxxxxx>
> > Signed-off-by: Luke Nelson <luke.r.nels@xxxxxxxxx>
> > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> > Acked-by: Wang YanQing <udknight@xxxxxxxxx>
> > Link: https://lore.kernel.org/bpf/20200422173630.8351-2-luke.r.nels@xxxxxxxxx
> > Signed-off-by: Wang YanQing <udknight@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx #v4.19
Now queued up, thanks.
greg k-h
