From 17de07163877d0f1fdd9185130ac4111f5f340f7 Mon Sep 17 00:00:00 2001 From: Michael Holzheu Date: Thu, 21 May 2015 15:39:31 +0200 Subject: s390/bpf: Fix backward jumps commit b035b60ded132592055c0f9bd1cc280259c7de4b upstream. Currently all backward jumps crash for JITed s390x eBPF programs with an illegal instruction program check and kernel panic. Because for negative values the opcode of the jump instruction is overriden by the negative branch offset an illegal instruction is generated by the JIT: 000003ff802da378: c01100000002 lgfi %r1,2 000003ff802da37e: fffffff52065 unknown <-- illegal instruction 000003ff802da384: b904002e lgr %r2,%r14 So fix this and mask the offset in order not to damage the opcode. Signed-off-by: Michael Holzheu Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- arch/s390/net/bpf_jit_comp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index 55423d8be580..9afb9d602f84 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -227,7 +227,7 @@ static inline void reg_set_seen(struct bpf_jit *jit, u32 b1) ({ \ /* Branch instruction needs 6 bytes */ \ int rel = (addrs[i + off + 1] - (addrs[i + 1] - 6)) / 2;\ - _EMIT6(op1 | reg(b1, b2) << 16 | rel, op2 | mask); \ + _EMIT6(op1 | reg(b1, b2) << 16 | (rel & 0xffff), op2 | mask); \ REG_SET_SEEN(b1); \ REG_SET_SEEN(b2); \ }) -- cgit v1.2.2