Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Daniel Borkmann says:

====================
pull-request: bpf 2018-04-25

The following pull-request contains BPF updates for your *net* tree.

The main changes are:

1) Fix to clear the percpu metadata_dst that could otherwise carry
   stale ip_tunnel_info, from William.

2) Fix that reduces the number of passes in x64 JIT with regards to
   dead code sanitation to avoid risk of prog rejection, from Gianluca.

3) Several fixes of sockmap programs, besides others, fixing a double
   page_put() in error path, missing refcount hold for pinned sockmap,
   adding required -target bpf for clang in sample Makefile, from John.

4) Fix to disable preemption in __BPF_PROG_RUN_ARRAY() paths, from Roman.

5) Fix tools/bpf/ Makefile with regards to a lex/yacc build error
   seen on older gcc-5, from John.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 1 deletions

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index b725154182cc3..abce27ceb411a 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1027,7 +1027,17 @@ emit_cond_jmp:		/* convert BPF opcode to x86 */
 			break;
 
 		case BPF_JMP | BPF_JA:
-			jmp_offset = addrs[i + insn->off] - addrs[i];
+			if (insn->off == -1)
+				/* -1 jmp instructions will always jump
+				 * backwards two bytes. Explicitly handling
+				 * this case avoids wasting too many passes
+				 * when there are long sequences of replaced
+				 * dead code.
+				 */
+				jmp_offset = -2;
+			else
+				jmp_offset = addrs[i + insn->off] - addrs[i];
+
 			if (!jmp_offset)
 				/* optimize out nop jumps */
 				break;