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bpf: Fix potential array overflow in bpf_trampoline_get_progs() 

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: 88fd9e5352 ("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>
This commit is contained in:
Yuntao Wang 2022-04-30 21:08:03 +08:00 committed by Alexei Starovoitov
parent 5790a2fee0
commit a2aa95b71c
1 changed files with 12 additions and 6 deletions
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18
kernel/bpf/trampoline.c
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@ -415,7 +415,7 @@ int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline
enum bpf_tramp_prog_type kind;
struct bpf_tramp_link *link_exiting;
int err = 0;
int cnt;
int cnt = 0, i;
kind = bpf_attach_type_to_tramp(link->link.prog);
mutex_lock(&tr->mutex);
@ -426,7 +426,10 @@ int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline
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