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[PATCH 4.6 43/81] s390/bpf: reduce maximum program size to 64 KB

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4.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Holzheu <holzheu@linux.vnet.ibm.com>

commit 0fa963553a5c28d8f8aabd8878326d3f782045fc upstream.

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")
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/s390/net/bpf_jit_comp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -45,7 +45,7 @@ struct bpf_jit {
 	int labels[1];		/* Labels for local jumps */
 };
 
-#define BPF_SIZE_MAX	0x7ffff	/* Max size for program (20 bit signed displ) */
+#define BPF_SIZE_MAX	0xffff	/* Max size for program (16 bit branches) */
 
 #define SEEN_SKB	1	/* skb access */
 #define SEEN_MEM	2	/* use mem[] for temporary storage */

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[PATCH 4.6 00/81] 4.6.3-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 12/81] ipv4: Fix non-initialized TTL when CONFIG_SYSCTL=n Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 25/81] l2tp: fix configuration passed to setup_udp_tunnel_sock() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 40/81] gpiolib: Fix NULL pointer deference Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 27/81] KVM: arm/arm64: vgic-v2: Clear all dirty LRs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 13/81] bpf, inode: disallow userns mounts Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 45/81] crypto: public_key: select CRYPTO_AKCIPHER Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 09/81] bpf: Use mount_nodev not mount_ns to mount the bpf filesystem Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 19/81] net: stmmac: Fix incorrect memcpy source memory Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 23/81] tcp: record TLP and ER timer stats in v6 stats Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 02/81] scsi: Add QEMU CD-ROM to VPD Inquiry Blacklist Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 43/81] s390/bpf: reduce maximum program size to 64 KB Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 28/81] KVM: arm/arm64: vgic-v3: Clear all dirty LRs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 15/81] net: hwbm: Fix unbalanced spinlock in error case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 08/81] tuntap: correctly wake up process during uninit Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 01:10 +0200
  [PATCH 4.6 00/87] 4.6.3-stable review -rc2 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-23 07:00 +0200
  Re: [PATCH 4.6 38/81] gpio: bail out silently on NULL descriptors Linus Walleij <linus.walleij@linaro.org> - 2016-06-23 09:30 +0200
    Re: [PATCH 4.6 38/81] gpio: bail out silently on NULL descriptors Hans de Goede <hdegoede@redhat.com> - 2016-06-23 11:20 +0200

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