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([36.24.59.242]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3112292c391sm4187402a91.0.2025.05.26.06.34.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 May 2025 06:34:25 -0700 (PDT) From: KaFai Wan To: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Cc: KaFai Wan , syzbot+0903f6d7f285e41cdf10@syzkaller.appspotmail.com Subject: [PATCH bpf-next 1/1] bpf: fix WARNING in __bpf_prog_ret0_warn when jit failed Date: Mon, 26 May 2025 21:33:58 +0800 Message-ID: <20250526133358.2594176-1-mannkafai@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit syzkaller reported an issue: WARNING: CPU: 3 PID: 217 at kernel/bpf/core.c:2357 __bpf_prog_ret0_warn+0xa/0x20 kernel/bpf/core.c:2357 Modules linked in: CPU: 3 UID: 0 PID: 217 Comm: kworker/u32:6 Not tainted 6.15.0-rc4-syzkaller-00040-g8bac8898fe39 #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Workqueue: ipv6_addrconf addrconf_dad_work RIP: 0010:__bpf_prog_ret0_warn+0xa/0x20 kernel/bpf/core.c:2357 RSP: 0018:ffffc900031f6c18 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffffc9000006e000 RCX: 1ffff9200000dc06 RDX: ffff8880234ba440 RSI: ffffffff81ca6979 RDI: ffff888031e93040 RBP: ffffc900031f6cb8 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff88802b61e010 R13: ffff888031e93040 R14: 00000000000000a0 R15: ffff88802c3d4800 FS: 0000000000000000(0000) GS:ffff8880d6ce2000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055557b6d2ca8 CR3: 000000002473e000 CR4: 0000000000352ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: bpf_dispatcher_nop_func include/linux/bpf.h:1316 [inline] __bpf_prog_run include/linux/filter.h:718 [inline] bpf_prog_run include/linux/filter.h:725 [inline] cls_bpf_classify+0x74a/0x1110 net/sched/cls_bpf.c:105 ... When creating bpf program, 'fp->jit_requested' depends on bpf_jit_enable. Currently the value of bpf_jit_enable is available from 0 to 2, 0 means use interpreter and not jit, 1 and 2 means need to jit. When CONFIG_BPF_JIT_ALWAYS_ON is enabled, bpf_jit_enable is permanently set to 1, when it's not set or disabled, we can set bpf_jit_enable via proc. This issue is triggered because of CONFIG_BPF_JIT_ALWAYS_ON is not set and bpf_jit_enable is set to 1, causing the arch to attempt JIT the prog, but jit failed due to FAULT_INJECTION. As a result, incorrectly treats the program as valid, when the program runs it calls `__bpf_prog_ret0_warn` and triggers the WARN_ON_ONCE(1). Reported-by: syzbot+0903f6d7f285e41cdf10@syzkaller.appspotmail.com Closes: https://lore.kernel.org/bpf/6816e34e.a70a0220.254cdc.002c.GAE@google.com Fixes: fa9dd599b4da ("bpf: get rid of pure_initcall dependency to enable jits") Signed-off-by: KaFai Wan --- kernel/bpf/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index a3e571688421..c20babbf998f 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2474,7 +2474,7 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err) /* In case of BPF to BPF calls, verifier did all the prep * work with regards to JITing, etc. */ - bool jit_needed = false; + bool jit_needed = fp->jit_requested; if (fp->bpf_func) goto finalize; -- 2.43.0