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[107.190.31.17]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d022a15199sm21124435ad.17.2026.07.29.23.30.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Jul 2026 23:30:48 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Thu, 30 Jul 2026 02:30:47 -0400 Message-Id: Subject: =?utf-8?q?Re:_[PATCH_bpf-next_v4]_bpf:_log_error_code_on_trampoline_unlin?= =?utf-8?q?k_failure=C2=A0?= From: "Emil Tsalapatis" To: , , , , , , , , , , , Cc: , X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20260729141159128mEJmS_aujBKr-cBu1p_UI@zte.com.cn> In-Reply-To: <20260729141159128mEJmS_aujBKr-cBu1p_UI@zte.com.cn> On Wed Jul 29, 2026 at 2:11 AM EDT, xu.xin16 wrote: > From: Xu Xin > > Replace silent WARN_ON_ONCE with WARN_ONCE that prints the actual error > code from bpf_trampoline_unlink_prog(). This aids debugging of race > conditions during link teardown, while keeping the warning rate limited > to avoid log flooding. > > This will be very helpful for speeding up trouble-shooting of some crash > UAF due to bpf_trampoline_unlink_prog failures. > > No change to unlink behavior. > > Signed-off-by: Xu Xin > Acked-by: Leon Hwang Reviewed-by: Emil Tsalapatis The Sashiko concern seems valid, please let me know if you are planning on looking into it otherwise I can take a look. > --- > Change log: > - Small fixes according to the v3 disccusion: > https://lore.kernel.org/all/82926caa-e16a-457a-8d75-61dfc8dac102@linux.= dev/ > > kernel/bpf/syscall.c | 8 +++++--- > kernel/bpf/trampoline.c | 12 ++++++++---- > 2 files changed, 13 insertions(+), 7 deletions(-) > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 6db306d23b47..52c57f8beb37 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -3626,10 +3626,12 @@ static void bpf_tracing_link_release(struct bpf_l= ink *link) > { > struct bpf_tracing_link *tr_link =3D > container_of(link, struct bpf_tracing_link, link.link); > + int err; > > - WARN_ON_ONCE(bpf_trampoline_unlink_prog(&tr_link->link.node, > - tr_link->trampoline, > - tr_link->tgt_prog)); > + err =3D bpf_trampoline_unlink_prog(&tr_link->link.node, > + tr_link->trampoline, > + tr_link->tgt_prog); > + WARN_ONCE(err, "bpf_trampoline_unlink_prog returns error: %d\n", err); > > bpf_trampoline_put(tr_link->trampoline); > > diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c > index 1a721fc4bef5..49dceea3d51e 100644 > --- a/kernel/bpf/trampoline.c > +++ b/kernel/bpf/trampoline.c > @@ -997,12 +997,15 @@ static void bpf_shim_tramp_link_release(struct bpf_= link *link) > { > struct bpf_shim_tramp_link *shim_link =3D > container_of(link, struct bpf_shim_tramp_link, link.link); > + int err; > > /* paired with 'shim_link->trampoline =3D tr' in bpf_trampoline_link_cg= roup_shim */ > if (!shim_link->trampoline) > return; > > - WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link.node, shim_lin= k->trampoline, NULL)); > + err =3D bpf_trampoline_unlink_prog(&shim_link->link.node, shim_link->tr= ampoline, NULL); > + WARN_ONCE(err, "bpf_trampoline_unlink_prog returns error: %d\n", err); > + > bpf_trampoline_put(shim_link->trampoline); > } > > @@ -1712,15 +1715,16 @@ int bpf_trampoline_multi_detach(struct bpf_prog *= prog, struct bpf_tracing_multi_ > { > struct bpf_tracing_multi_data *data =3D &link->data; > struct bpf_tracing_multi_node *mnode; > - int i; > + int i, err; > > trampoline_lock_all(); > > for_each_mnode(mnode, link) { > data->entry =3D &mnode->entry; > bpf_trampoline_multi_attach_init(mnode->trampoline); > - WARN_ON_ONCE(__bpf_trampoline_unlink_prog(&mnode->node, mnode->trampol= ine, > - NULL, &trampoline_multi_ops, data)); > + err =3D __bpf_trampoline_unlink_prog(&mnode->node, mnode->trampoline, = NULL, > + &trampoline_multi_ops, data); > + WARN_ONCE(err, "__bpf_trampoline_unlink_prog returns error: %d\n", err= ); > } > > if (ftrace_hash_count(data->unreg))