net: filter: add jited flag to indicate jit compiled filters

This patch adds a jited flag into sk_filter struct in order to indicate
whether a filter is currently jited or not. The size of sk_filter is
not being expanded as the 32 bit 'len' member allows upper bits to be
reused since a filter can currently only grow as large as BPF_MAXINSNS.

Therefore, there's enough room also for other in future needed flags to
reuse 'len' field if necessary. The jited flag also allows for having
alternative interpreter functions running as currently, we can only
detect jit compiled filters by testing fp->bpf_func to not equal the
address of sk_run_filter().

Joint work with Alexei Starovoitov.

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 153f8f2cfd56..9c36dc398f90 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -877,6 +877,7 @@ void bpf_jit_compile(struct sk_filter *fp)
         if (jit.start) {
                 set_memory_ro((unsigned long)header, header->pages);
                 fp->bpf_func = (void *) jit.start;
+                fp->jited = 1;
         }
 out:
         kfree(addrs);
@@ -887,10 +888,12 @@ void bpf_jit_free(struct sk_filter *fp)
         unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK;
         struct bpf_binary_header *header = (void *)addr;
 
-        if (fp->bpf_func == sk_run_filter)
+        if (!fp->jited)
                 goto free_filter;
+
         set_memory_rw(addr, header->pages);
         module_free(NULL, header);
+
 free_filter:
         kfree(fp);
 }