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Tue, 21 Oct 2025 02:56:07 -0700 (PDT) Date: Tue, 21 Oct 2025 02:56:06 -0700 In-Reply-To: <68f6a4c8.050a0220.1be48.0011.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <68f758b6.050a0220.346f24.000c.GAE@google.com> Subject: Forwarded: Re: [syzbot] [bpf?] WARNING in bpf_bprintf_prepare (3) From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: Re: [syzbot] [bpf?] WARNING in bpf_bprintf_prepare (3) Author: listout@listout.xyz On 20.10.2025 14:08, syzbot wrote: > Hello, >=20 > syzbot found the following issue on: >=20 > HEAD commit: a1e83d4c0361 selftests/bpf: Fix redefinition of 'off' as = d.. > git tree: bpf > console output: https://syzkaller.appspot.com/x/log.txt?x=3D12d21de2580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=3D9ad7b090a1865= 4a7 > dashboard link: https://syzkaller.appspot.com/bug?extid=3Db0cff308140f79a= 9c4cb > compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b797= 6-1~exp1~20250708183702.136), Debian LLD 20.1.8 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=3D160cf542580= 000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=3D128d5c58580000 >=20 > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/2f6a7a0cd1b7/dis= k-a1e83d4c.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/873984cfc71e/vmlinu= x-a1e83d4c.xz > kernel image: https://storage.googleapis.com/syzbot-assets/16711d84070c/b= zImage-a1e83d4c.xz >=20 > The issue was bisected to: >=20 > commit 7c33e97a6ef5d84e98b892c3e00c6d1678d20395 > Author: Sahil Chandna > Date: Tue Oct 14 18:56:35 2025 +0000 >=20 > bpf: Do not disable preemption in bpf_test_run(). >=20 > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=3D172fe49258= 0000 > final oops: https://syzkaller.appspot.com/x/report.txt?x=3D14afe49258= 0000 > console output: https://syzkaller.appspot.com/x/log.txt?x=3D10afe492580000 >=20 > IMPORTANT: if you fix the issue, please add the following tag to the comm= it: > Reported-by: syzbot+b0cff308140f79a9c4cb@syzkaller.appspotmail.com > Fixes: 7c33e97a6ef5 ("bpf: Do not disable preemption in bpf_test_run().") #syz test diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 8b7d0b90fea7..cc4288f408f2 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -36,7 +36,8 @@ struct bpf_test_timer { static void bpf_test_timer_enter(struct bpf_test_timer *t) __acquires(rcu) { - rcu_read_lock_dont_migrate(); + rcu_read_lock(); + migrate_disable(); t->time_start =3D ktime_get_ns(); } =20 @@ -44,7 +45,8 @@ static void bpf_test_timer_leave(struct bpf_test_timer *t) __releases(rcu) { t->time_start =3D 0; - rcu_read_unlock_migrate(); + migrate_enable(); + rcu_read_unlock(); } =20 static bool bpf_test_timer_continue(struct bpf_test_timer *t, int iteratio= ns, --=20 Regards, listout