bpf: consolidate bpf_prog_put{, _rcu} dismantle paths

We currently have duplicated cleanup code in bpf_prog_put() and
bpf_prog_put_rcu() cleanup paths. Back then we decided that it was
not worth it to make it a common helper called by both, but with
the recent addition of resource charging, we could have avoided
the fix in commit ac00737f4e81 ("bpf: Need to call bpf_prog_uncharge_memlock
from bpf_prog_put") if we would have had only a single, common path.
We can simplify it further by assigning aux->prog only once during
allocation time.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 7 insertions, 11 deletions

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 80864712d2c4..334b1bdd572c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -92,6 +92,7 @@ struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags)
 
         fp->pages = size / PAGE_SIZE;
         fp->aux = aux;
+        fp->aux->prog = fp;
 
         return fp;
 }
@@ -116,6 +117,7 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
 
                 memcpy(fp, fp_old, fp_old->pages * PAGE_SIZE);
                 fp->pages = size / PAGE_SIZE;
+                fp->aux->prog = fp;
 
                 /* We keep fp->aux from fp_old around in the new
                  * reallocated structure.
@@ -726,7 +728,6 @@ void bpf_prog_free(struct bpf_prog *fp)
         struct bpf_prog_aux *aux = fp->aux;
 
         INIT_WORK(&aux->work, bpf_prog_free_deferred);
-        aux->prog = fp;
         schedule_work(&aux->work);
 }
 EXPORT_SYMBOL_GPL(bpf_prog_free);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 3fff82ca68fa..d7783cb04d86 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -513,7 +513,7 @@ static void bpf_prog_uncharge_memlock(struct bpf_prog *prog)
         free_uid(user);
 }
 
-static void __prog_put_rcu(struct rcu_head *rcu)
+static void __prog_put_common(struct rcu_head *rcu)
 {
         struct bpf_prog_aux *aux = container_of(rcu, struct bpf_prog_aux, rcu);
 
@@ -525,19 +525,14 @@ static void __prog_put_rcu(struct rcu_head *rcu)
 /* version of bpf_prog_put() that is called after a grace period */
 void bpf_prog_put_rcu(struct bpf_prog *prog)
 {
-        if (atomic_dec_and_test(&prog->aux->refcnt)) {
-                prog->aux->prog = prog;
-                call_rcu(&prog->aux->rcu, __prog_put_rcu);
-        }
+        if (atomic_dec_and_test(&prog->aux->refcnt))
+                call_rcu(&prog->aux->rcu, __prog_put_common);
 }
 
 void bpf_prog_put(struct bpf_prog *prog)
 {
-        if (atomic_dec_and_test(&prog->aux->refcnt)) {
-                free_used_maps(prog->aux);
-                bpf_prog_uncharge_memlock(prog);
-                bpf_prog_free(prog);
-        }
+        if (atomic_dec_and_test(&prog->aux->refcnt))
+                __prog_put_common(&prog->aux->rcu);
 }
 EXPORT_SYMBOL_GPL(bpf_prog_put);