[PATCH 5.17 69/75] bpf: Fix potential array overflow in bpf_trampoline_get_progs()

Greg Kroah-Hartman
2022-06-03T18:16:52Z

From: Yuntao Wang <ytcoode@gmail.com>

commit a2aa95b71c9bbec793b5c5fa50f0a80d882b3e8d upstream.

The cnt value in the 'cnt >= BPF_MAX_TRAMP_PROGS' check does not
include BPF_TRAMP_MODIFY_RETURN bpf programs, so the number of
the attached BPF_TRAMP_MODIFY_RETURN bpf programs in a trampoline
can exceed BPF_MAX_TRAMP_PROGS.

When this happens, the assignment '*progs++ = aux->prog' in
bpf_trampoline_get_progs() will cause progs array overflow as the
progs field in the bpf_tramp_progs struct can only hold at most
BPF_MAX_TRAMP_PROGS bpf programs.

Fixes: 88fd9e5352fe ("bpf: Refactor trampoline update code")
Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Link: https://lore.kernel.org/r/20220430130803.210624-1-ytcoode@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/bpf/trampoline.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)

--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -423,7 +423,7 @@ int bpf_trampoline_link_prog(struct bpf_
{
enum bpf_tramp_prog_type kind;
int err = 0;
- int cnt;
+ int cnt = 0, i;

kind = bpf_attach_type_to_tramp(prog);
mutex_lock(&tr->mutex);
@@ -434,7 +434,10 @@ int bpf_trampoline_link_prog(struct bpf_
err = -EBUSY;
goto out;
}
- cnt = tr->progs_cnt[BPF_TRAMP_FENTRY] + tr->progs_cnt[BPF_TRAMP_FEXIT];
+
+ for (i = 0; i < BPF_TRAMP_MAX; i++)
+ cnt += tr->progs_cnt[i];
+
if (kind == BPF_TRAMP_REPLACE) {
/* Cannot attach extension if fentry/fexit are in use. */
if (cnt) {
@@ -512,16 +515,19 @@ out:

void bpf_trampoline_put(struct bpf_trampoline *tr)
{
+ int i;
+
if (!tr)
return;
mutex_lock(&trampoline_mutex);
if (!refcount_dec_and_test(&tr->refcnt))
goto out;
WARN_ON_ONCE(mutex_is_locked(&tr->mutex));
- if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[BPF_TRAMP_FENTRY])))
- goto out;
- if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[BPF_TRAMP_FEXIT])))
- goto out;
+
+ for (i = 0; i < BPF_TRAMP_MAX; i++)
+ if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[i])))
+ goto out;
+
/* This code will be executed even when the last bpf_tramp_image
* is alive. All progs are detached from the trampoline and the
* trampoline image is patched with jmp into epilogue to skip