s390/bpf: reduce maximum program size to 64 KB
authorMichael Holzheu <holzheu@linux.vnet.ibm.com>
Thu, 12 May 2016 16:10:48 +0000 (18:10 +0200)
committerMartin Schwidefsky <schwidefsky@de.ibm.com>
Thu, 19 May 2016 07:14:27 +0000 (09:14 +0200)
commit0fa963553a5c28d8f8aabd8878326d3f782045fc
treea16902f8f6f8182a72bff270e415ac9aed4a9cf2
parent2600a46ee0ed57c0e0a382c2a37ebac64d374d20
s390/bpf: reduce maximum program size to 64 KB

The s390 BFP compiler currently uses relative branch instructions
that only support jumps up to 64 KB. Examples are "j", "jnz", "cgrj",
etc.  Currently the maximum size of s390 BPF programs is set
to 0x7ffff.  If branches over 64 KB are generated the, kernel can
crash due to incorrect code.

So fix this an reduce the maximum size to 64 KB. Programs larger than
that will be interpreted.

Fixes: ce2b6ad9c185 ("s390/bpf: increase BPF_SIZE_MAX")

Cc: stable@vger.kernel.org # 4.3+
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
arch/s390/net/bpf_jit_comp.c