From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-il1-f205.google.com (mail-il1-f205.google.com [209.85.166.205]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 52DE525229C for ; Mon, 4 Aug 2025 11:12:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.166.205 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754305959; cv=none; b=q8i2pBJZ9Dq6VhSynKy4cRf/R9J/6rH/RqVkFwfnAmrgJEhuPDWx4ULFGYy9fL3E/0h2xjYCah1O4P0FTgjvBTfI72Dhha+zyO+1aAHaZt4GBX9/Av8gwX5WljGuTyaqIZlHqpe++TTPcOQvfrQ7V8h4/ECudifQckMMfvpTnVM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754305959; c=relaxed/simple; bh=sS1YT27CJtLoZAmprfV76F5Z1H4mkr6BMsHwJXvAoaE=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=tqofbKrPBw73lS2jZoiCQlT7942zPzG9fVHSpkP6Ek8NJGnFj+znj9JHivKzMpHYnZ47vtSsn7oMQyP8wymZwPKA6YmjCcrHHWo+KHV3yVE/OOMKCxn2Lx9TWaByZ0UNLPefPq2WbCsc6rjHCq5F7dRZzrcQONxRBLdfwjHGJs4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.166.205 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-il1-f205.google.com with SMTP id e9e14a558f8ab-3e3d462b81cso39177985ab.3 for ; Mon, 04 Aug 2025 04:12:37 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754305957; x=1754910757; h=to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=UZC4QBhhXxtpdVYVwy1WTCm0gMYAELnv1sLEfnwbWNs=; b=UiKsQ25btWoOmJvDHMaPnDVVdbB38h6ZEiwCGXI4GTGNB0V1v+cHNsZ5woQ9UX1Q8d BIFL+Ipffr6G9+jF0McA+cySjZfzJSQlTFsWZ1yLPRwX508YVBRisC4t6DaQnZpXeD2S FUCPiU3Xapdgfx8I+CuA4W1FduNEyBAQHRInD6URHv47cwBHtEL/5BGTV0UqRApVZuQJ nZVKMeqBOTcjQCxu7TIyUqjpiL2DjUOHEdnrxazp3SQ4PwabqkjdIFc2KAAuD0t9vmwq cyaIEObwrRVzXPrc6HtpJwqe41OP4AEbJmS7GTqXirJR7sco6G0gVtSjQK1km3jxkmag 6dCQ== X-Forwarded-Encrypted: i=1; AJvYcCUIrTeVAeisGdkORmpjn5PtGN/gR0+nyA/F+522EuHPg9sTSn0mvEN0pNsJGqn/hm0wk5TuN+E=@vger.kernel.org X-Gm-Message-State: AOJu0Yw+47t88suKFJjylsDNPHbRa7SfPOTrpNcEmAcL8oJDm0ZEdz16 Q83WFVz8X/pxNYYUtKr0malYs+g69Hb5ZJ/tszBmA3/PtQGjIrhg7W5AFigPTlnngZqw5rcNpKO uy+ckB6usfWPrBn4BstUKJwagU9dRKcXTdKCag5ndxBxL5iMyjShBnrLPBi0= X-Google-Smtp-Source: AGHT+IFs9AdaOr2KbRyq2uBDNXmOAIq8TzhwKVvLOht03tvjs458CeoUQyq9O7YmYPMbVMr1ReGGRU26aXBDZrwwvDoEz4HNoivk Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6e02:1f0d:b0:3e3:f1db:d352 with SMTP id e9e14a558f8ab-3e41616f18amr165903325ab.15.1754305957281; Mon, 04 Aug 2025 04:12:37 -0700 (PDT) Date: Mon, 04 Aug 2025 04:12:37 -0700 In-Reply-To: <67f66c9c.050a0220.25d1c8.0003.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <689095a5.050a0220.1fc43d.0009.GAE@google.com> Subject: Re: [syzbot] [net?] KASAN: null-ptr-deref Write in rcuref_put (4) From: syzbot To: davem@davemloft.net, edumazet@google.com, horms@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: 5c5a10f0be96 Add linux-next specific files for 20250804 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=14f23aa2580000 kernel config: https://syzkaller.appspot.com/x/.config?x=f4ccbd076877954b dashboard link: https://syzkaller.appspot.com/bug?extid=27d7cfbc93457e472e00 compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1628faa2580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12490434580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/cb2134de7be8/disk-5c5a10f0.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/fe8a36605e0c/vmlinux-5c5a10f0.xz kernel image: https://storage.googleapis.com/syzbot-assets/12df22603d55/bzImage-5c5a10f0.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+27d7cfbc93457e472e00@syzkaller.appspotmail.com BUG: unable to handle page fault for address: ffffffffffffffdb #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD df3b067 P4D df3b067 PUD df3d067 PMD 0 Oops: Oops: 0002 [#1] SMP KASAN PTI CPU: 1 UID: 0 PID: 6346 Comm: syz.0.336 Not tainted 6.16.0-next-20250804-syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:arch_atomic_add_return arch/x86/include/asm/atomic.h:85 [inline] RIP: 0010:raw_atomic_sub_return_release include/linux/atomic/atomic-arch-fallback.h:846 [inline] RIP: 0010:atomic_sub_return_release include/linux/atomic/atomic-instrumented.h:327 [inline] RIP: 0010:__rcuref_put include/linux/rcuref.h:109 [inline] RIP: 0010:rcuref_put+0x172/0x210 include/linux/rcuref.h:173 Code: c7 c7 80 72 94 8c be 68 00 00 00 48 c7 c2 c0 72 94 8c e8 21 f7 35 f8 48 89 df be 04 00 00 00 e8 84 90 bb f8 41 be ff ff ff ff 44 0f c1 33 41 8d 76 ff bf ff ff ff ff e8 ab 27 58 f8 41 ff ce RSP: 0018:ffffc9000431f960 EFLAGS: 00010256 RAX: ffffffff89678f01 RBX: ffffffffffffffdb RCX: ffffffff89678fdc RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffffffffffffdb RBP: ffffc9000431f9f8 R08: ffffffffffffffde R09: 1ffffffffffffffb R10: dffffc0000000000 R11: fffffbfffffffffc R12: dffffc0000000000 R13: dffffc0000000000 R14: 00000000ffffffff R15: 1ffff92000863f2c FS: 0000555583637500(0000) GS:ffff888125d17000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffdb CR3: 000000002465a000 CR4: 00000000003526f0 Call Trace: dst_release+0x24/0x1b0 net/core/dst.c:167 ip_rt_put include/net/route.h:285 [inline] pptp_xmit+0x14b/0x1a90 drivers/net/ppp/pptp.c:267 __ppp_channel_push+0xf2/0x1c0 drivers/net/ppp/ppp_generic.c:2166 ppp_channel_push+0x123/0x660 drivers/net/ppp/ppp_generic.c:2198 ppp_write+0x2b0/0x400 drivers/net/ppp/ppp_generic.c:544 vfs_write+0x27b/0xb30 fs/read_write.c:684 ksys_write+0x145/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fda7098eb69 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fffb2fc7658 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fda70bb5fa0 RCX: 00007fda7098eb69 RDX: 0000000000000013 RSI: 00002000000002c0 RDI: 0000000000000004 RBP: 00007fda70a11df1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fda70bb5fa0 R14: 00007fda70bb5fa0 R15: 0000000000000003 Modules linked in: CR2: ffffffffffffffdb ---[ end trace 0000000000000000 ]--- RIP: 0010:arch_atomic_add_return arch/x86/include/asm/atomic.h:85 [inline] RIP: 0010:raw_atomic_sub_return_release include/linux/atomic/atomic-arch-fallback.h:846 [inline] RIP: 0010:atomic_sub_return_release include/linux/atomic/atomic-instrumented.h:327 [inline] RIP: 0010:__rcuref_put include/linux/rcuref.h:109 [inline] RIP: 0010:rcuref_put+0x172/0x210 include/linux/rcuref.h:173 Code: c7 c7 80 72 94 8c be 68 00 00 00 48 c7 c2 c0 72 94 8c e8 21 f7 35 f8 48 89 df be 04 00 00 00 e8 84 90 bb f8 41 be ff ff ff ff 44 0f c1 33 41 8d 76 ff bf ff ff ff ff e8 ab 27 58 f8 41 ff ce RSP: 0018:ffffc9000431f960 EFLAGS: 00010256 RAX: ffffffff89678f01 RBX: ffffffffffffffdb RCX: ffffffff89678fdc RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffffffffffffdb RBP: ffffc9000431f9f8 R08: ffffffffffffffde R09: 1ffffffffffffffb R10: dffffc0000000000 R11: fffffbfffffffffc R12: dffffc0000000000 R13: dffffc0000000000 R14: 00000000ffffffff R15: 1ffff92000863f2c FS: 0000555583637500(0000) GS:ffff888125d17000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffdb CR3: 000000002465a000 CR4: 00000000003526f0 ---------------- Code disassembly (best guess): 0: c7 c7 80 72 94 8c mov $0x8c947280,%edi 6: be 68 00 00 00 mov $0x68,%esi b: 48 c7 c2 c0 72 94 8c mov $0xffffffff8c9472c0,%rdx 12: e8 21 f7 35 f8 call 0xf835f738 17: 48 89 df mov %rbx,%rdi 1a: be 04 00 00 00 mov $0x4,%esi 1f: e8 84 90 bb f8 call 0xf8bb90a8 24: 41 be ff ff ff ff mov $0xffffffff,%r14d * 2a: f0 44 0f c1 33 lock xadd %r14d,(%rbx) <-- trapping instruction 2f: 41 8d 76 ff lea -0x1(%r14),%esi 33: bf ff ff ff ff mov $0xffffffff,%edi 38: e8 ab 27 58 f8 call 0xf85827e8 3d: 41 ff ce dec %r14d --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing.