From nobody Sat Feb 7 21:15:48 2026 Received: from mail-oa1-f77.google.com (mail-oa1-f77.google.com [209.85.160.77]) (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 59F8A2264AA for ; Sun, 18 Jan 2026 21:55:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.77 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768773303; cv=none; b=M7YAdfvBWEINCWSDw3VPwTvZJXfjlwbW5bKZSFze1OXthgqCpzsYoNQELrD0xArtlbjarDidB+XomiKxmDX8aY+0ajRHaFRzAKp75VncSaJriCVNjJX+9ALOyUlz/I1mtSVpAh1emBC+LVcXSkk5O5mnhmm00/X5xYfqrRPun1A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768773303; c=relaxed/simple; bh=+ija22KDPDhs2wdIt39A6YrINmO+mckUTXDOVXlF0pc=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=XhrbqWPKl+EdfUh4fN0Zd6akIPREtTct7Z7Q1z2P26BDeT3I8xh/nVuZxs1NPLGJB9Kd0SsZqTWRU5CfkJFyvuTFggVlsb81ft0Dw2sNSo8ywfpxDF2V2MnZBvJa+Co92KZoMqdUyjrvUI33B7uw3erEqdzfk0AyZFRGSd5B560= 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=209.85.160.77 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-oa1-f77.google.com with SMTP id 586e51a60fabf-40418f60513so8189706fac.2 for ; Sun, 18 Jan 2026 13:55:01 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1768773300; x=1769378100; 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=QTBBbs/mN2SOaE0eOdcLrrPoFn+5eT3sNmDkBs1btn4=; b=jLTcx/kW0/3zZs/GfJ4gmJVDlN5lE2iS0a0TX9PiJ9xH6vepYHki0VOxdZ0g59865x 6G6m/3pYWUMtNiYbbcR37bXunom49NcE5UrB6SOu++GIEvcjgniR66AH7LU5J6/Hc4yE W5X1Hz8lb+hvWMytgAwrKzwssIrumJXcPF09X1kk4+THlGTnIGldM79TBeKb2To/uy0m SGD8986S/9XniHduXzLzjnkMydHPWZ5wWvpA8D9zqJPgspwAdIQkLzwufAE3MT1x8tmu lPqqogpVj8yAXBjzJDCng7cfGethlqCRBnHBdVxNp+/1Y5eWS4+82kTkYMg4VG1Xb8tg LEGQ== X-Gm-Message-State: AOJu0YxZay5o8HVNHTGLAzvhUMnrJg/SEBMvvyR1ESJSQzTRpsKJ5oGI S4X4uaLwq6z8tAFRdOvEICElovo+5vg/vezHSNWIfesTzG2q03H3jc98vWefXu4IhCrvcl7q9Oi DHVq3y0WVKliAjGNltE1agaQOJ6KQYE+nqDNJk9Em9qM7CnHI4SGULMgYhdle9w== Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a4a:bb17:0:b0:661:1cbc:45c2 with SMTP id 006d021491bc7-6611cbc4928mr2636256eaf.16.1768773300212; Sun, 18 Jan 2026 13:55:00 -0800 (PST) Date: Sun, 18 Jan 2026 13:55:00 -0800 In-Reply-To: <66e96979.050a0220.252d9a.000a.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <696d56b4.050a0220.3390f1.0027.GAE@google.com> Subject: Forwarded: Private message regarding: [syzbot] [mm?] INFO: rcu detected stall in sys_execve (6) 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: Private message regarding: [syzbot] [mm?] INFO: rcu detected stall= in sys_execve (6) Author: kapoorarnav43@gmail.com #syz test From 4e8268fd6319d5b97ba6334b7f66fd0b1719b863 Mon Sep 17 00:00:00 2001 From: Arnav Kapoor Date: Mon, 19 Jan 2026 03:15:46 +0530 Subject: [PATCH] fs/exec: add cond_resched() in setup_arg_pages to prevent=20 RCU stalls Syzbot reported an RCU stall in sys_execve. The issue occurs when setup_arg_pages() calls expand_stack_locked() which can perform memory allocations that take significant time without yielding to the scheduler. This prevents RCU grace periods from completing, leading to RCU stalls. The fix is minimal: add cond_resched() after expand_stack_locked() returns, allowing the scheduler to preempt if needed and permitting RCU grace periods to complete. Reported-by: syzbot+af59ca6e6cfb5db2946e165031b25d7f52ee60e9 Closes:=20 https://syzkaller.appspot.com/bug?id=3Daf59ca6e6cfb5db2946e165031b25d7f52ee= 60e9 Signed-off-by: Arnav Kapoor Reported-by: syzbot+8bb3e2...@syzkaller.appspotmail.com=20 --- fs/exec.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/exec.c b/fs/exec.c index 9d5ebc9d1..fb7ae929d 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -712,6 +712,8 @@ int setup_arg_pages(struct linux_binprm *bprm, #endif current->mm->start_stack =3D bprm->p; ret =3D expand_stack_locked(vma, stack_base); + /* Allow RCU and scheduler to make progress. */ + cond_resched(); if (ret) ret =3D -EFAULT; =20 --=20 2.43.0 On Sunday, 18 January 2026 at 04:48:24 UTC+5:30 syzbot wrote: syzbot has found a reproducer for the following issue on:=20 HEAD commit: a74c7a58ca2c net: freescale: ucc_geth: Return early when T..=20 git tree: net=20 console output: https://syzkaller.appspot.com/x/log.txt?x=3D16fdf39a580000=20 kernel config: https://syzkaller.appspot.com/x/.config?x=3D323fe5bdde2384a5=20 dashboard link: https://syzkaller.appspot.com/bug?extid=3D8bb3e2bee8a429cc7= 6dd=20 compiler: Debian clang version 20.1.8=20 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD=20 20.1.8=20 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=3D13d8639a580000=20 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=3D154863fa580000=20 Downloadable assets:=20 disk image:=20 https://storage.googleapis.com/syzbot-assets/50a3e60a3908/disk-a74c7a58.raw= .xz=20 vmlinux:=20 https://storage.googleapis.com/syzbot-assets/ee6a6a2a52e4/vmlinux-a74c7a58.= xz=20 kernel image:=20 https://storage.googleapis.com/syzbot-assets/033a07d12b3e/bzImage-a74c7a58.= xz=20 The issue was bisected to:=20 commit 5a781ccbd19e4664babcbe4b4ead7aa2b9283d22=20 Author: Vinicius Costa Gomes =20 Date: Sat Sep 29 00:59:43 2018 +0000=20 tc: Add support for configuring the taprio scheduler=20 bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=3D1031190058000= 0=20 final oops: https://syzkaller.appspot.com/x/report.txt?x=3D12311900580000=20 console output: https://syzkaller.appspot.com/x/log.txt?x=3D14311900580000=20 IMPORTANT: if you fix the issue, please add the following tag to the=20 commit:=20 Reported-by: syzbot+8bb3e2...@syzkaller.appspotmail.com=20 Fixes: 5a781ccbd19e ("tc: Add support for configuring the taprio=20 scheduler")=20 rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:=20 rcu: 1-...!: (1 GPs behind) idle=3Db674/1/0x4000000000000000=20 softirq=3D16193/16205 fqs=3D2=20 rcu: (detected by 0, t=3D10502 jiffies, g=3D13757, q=3D3905 ncpus=3D2)=20 Sending NMI from CPU 0 to CPUs 1:=20 NMI backtrace for cpu 1=20 CPU: 1 UID: 0 PID: 6128 Comm: syz-executor Not tainted syzkaller #0=20 PREEMPT(full)=20 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS=20 Google 10/25/2025=20 RIP: 0010:rcu_is_watching_curr_cpu include/linux/context_tracking.h:128=20 [inline]=20 RIP: 0010:rcu_is_watching+0x3a/0xb0 kernel/rcu/tree.c:751=20 Code: e8 bb 0d b3 09 89 c3 83 f8 08 73 65 49 bf 00 00 00 00 00 fc ff df 4c=20 8d 34 dd d0 0d 9b 8d 4c 89 f0 48 c1 e8 03 42 80 3c 38 00 <74> 08 4c 89 f7=20 e8 8c 1d 80 00 48 c7 c3 d8 56 81 92 49 03 1e 48 89=20 RSP: 0018:ffffc90000a08c70 EFLAGS: 00000046=20 RAX: 1ffffffff1b361bb RBX: 0000000000000001 RCX: 0000000000010002=20 RDX: 0000000000000000 RSI: ffffffff8bc086c0 RDI: ffffffff8bc08680=20 RBP: ffffffff81ae6da2 R08: 0000000000000001 R09: 0000000000000000=20 R10: dffffc0000000000 R11: fffffbfff1f045cf R12: 0000000000000000=20 R13: ffff8880b8728258 R14: ffffffff8d9b0dd8 R15: dffffc0000000000=20 FS: 0000000000000000(0000) GS:ffff888125f1e000(0000) knlGS:0000000000000000=20 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033=20 CR2: 00007f9426807ff8 CR3: 0000000077a18000 CR4: 00000000003526f0=20 Call Trace:=20 =20 trace_lock_acquire include/trace/events/lock.h:24 [inline]=20 lock_acquire+0x5f/0x340 kernel/locking/lockdep.c:5831=20 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]=20 _raw_spin_lock_irq+0x3d/0x50 kernel/locking/spinlock.c:170=20 __run_hrtimer kernel/time/hrtimer.c:1781 [inline]=20 __hrtimer_run_queues+0x5e2/0xc30 kernel/time/hrtimer.c:1841=20 hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1903=20 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]=20 __sysvec_apic_timer_interrupt+0x102/0x3e0 arch/x86/kernel/apic/apic.c:1062=20 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]=20 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1056=20 =20 =20 asm_sysvec_apic_timer_interrupt+0x1a/0x20=20 arch/x86/include/asm/idtentry.h:697=20 RIP: 0010:deref_stack_reg+0x3/0x230 arch/x86/kernel/unwind_orc.c:418=20 Code: e8 12 f8 b2 00 48 8b 4c 24 18 e9 f2 fe ff ff 0f 1f 84 00 00 00 00 00=20 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 55 41 57 <41> 56 41 55 41=20 54 53 48 83 ec 20 48 89 54 24 18 49 89 f0 49 89 ff=20 RSP: 0018:ffffc90002f16e00 EFLAGS: 00000283=20 RAX: fffffffffffffff0 RBX: ffffffff9025420e RCX: 0000000000000000=20 RDX: ffffc90002f16f28 RSI: ffffc90002f17ad0 RDI: ffffc90002f16ee8=20 RBP: dffffc0000000000 R08: ffffc90002f16f47 R09: 0000000000000000=20 R10: ffffc90002f16f38 R11: fffff520005e2de9 R12: ffffc90002f16f38=20 R13: 1ffff920005e2ddf R14: ffffc90002f16ee8 R15: 1ffffffff204a842=20 unwind_next_frame+0x18cc/0x23d0 arch/x86/kernel/unwind_orc.c:-1=20 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25=20 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122=20 kasan_save_stack mm/kasan/common.c:57 [inline]=20 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78=20 unpoison_slab_object mm/kasan/common.c:340 [inline]=20 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366=20 kasan_slab_alloc include/linux/kasan.h:253 [inline]=20 slab_post_alloc_hook mm/slub.c:4953 [inline]=20 slab_alloc_node mm/slub.c:5263 [inline]=20 kmem_cache_alloc_noprof+0x37d/0x710 mm/slub.c:5270=20 mt_alloc_one lib/maple_tree.c:174 [inline]=20 mas_alloc_nodes+0x291/0x350 lib/maple_tree.c:1110=20 mas_preallocate+0x2e0/0x670 lib/maple_tree.c:5194=20 vma_iter_prealloc mm/vma.h:502 [inline]=20 vma_shrink+0x18d/0x510 mm/vma.c:1200=20 relocate_vma_down+0x4d4/0x4f0 mm/vma_exec.c:91=20 setup_arg_pages+0x5cf/0xa90 fs/exec.c:690=20 load_elf_binary+0xba4/0x2740 fs/binfmt_elf.c:1028=20 search_binary_handler fs/exec.c:1669 [inline]=20 exec_binprm fs/exec.c:1701 [inline]=20 bprm_execve+0x92e/0x1400 fs/exec.c:1753=20 do_execveat_common+0x510/0x6a0 fs/exec.c:1859=20 do_execve fs/exec.c:1933 [inline]=20 __do_sys_execve fs/exec.c:2009 [inline]=20 __se_sys_execve fs/exec.c:2004 [inline]=20 __x64_sys_execve+0x94/0xb0 fs/exec.c:2004=20 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]=20 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94=20 entry_SYSCALL_64_after_hwframe+0x77/0x7f=20 RIP: 0033:0x7f94259c2e17=20 Code: Unable to access opcode bytes at 0x7f94259c2ded.=20 RSP: 002b:00007f9426807df8 EFLAGS: 00000206 ORIG_RAX: 000000000000003b=20 RAX: ffffffffffffffda RBX: 00007ffd48e33ef5 RCX: 00007f94259c2e17=20 RDX: 00007ffd48e32ba0 RSI: 00007ffd48e32de0 RDI: 00007ffd48e33ef5=20 RBP: 00007f9426807e70 R08: 00007f9426807f20 R09: 0000000000000000=20 R10: 0000000000000008 R11: 0000000000000206 R12: 00007ffd48e32de0=20 R13: 00007ffd48e32ba0 R14: 0000000000000000 R15: 0000000000000000=20 =20 rcu: rcu_preempt kthread starved for 10495 jiffies! g13757 f0x0=20 RCU_GP_WAIT_FQS(5) ->state=3D0x0 ->cpu=3D0=20 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now=20 expected behavior.=20 rcu: RCU grace-period kthread stack dump:=20 task:rcu_preempt state:R running task stack:27480 pid:16 tgid:16 ppid:2=20 task_flags:0x208040 flags:0x00080000=20 Call Trace:=20 =20 context_switch kernel/sched/core.c:5256 [inline]=20 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863=20 __schedule_loop kernel/sched/core.c:6945 [inline]=20 schedule+0x165/0x360 kernel/sched/core.c:6960=20 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99=20 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083=20 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285=20 kthread+0x711/0x8a0 kernel/kthread.c:463=20 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158=20 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246=20 =20 rcu: Stack dump where RCU GP kthread last ran:=20 CPU: 0 UID: 0 PID: 5203 Comm: udevd Not tainted syzkaller #0 PREEMPT(full)=20 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS=20 Google 10/25/2025=20 RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline]=20 RIP: 0010:smp_call_function_many_cond+0xcc5/0x1260 kernel/smp.c:877=20 Code: 45 8b 2c 24 44 89 ee 83 e6 01 31 ff e8 d4 97 0b 00 41 83 e5 01 49 bd=20 00 00 00 00 00 fc ff df 75 07 e8 7f 93 0b 00 eb 38 f3 90 <42> 0f b6 04 2b=20 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 63 93=20 RSP: 0000:ffffc90003057820 EFLAGS: 00000293=20 RAX: ffffffff81b5654d RBX: 1ffff110170e8129 RCX: ffff88807d153d00=20 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000=20 RBP: ffffc90003057950 R08: ffffffff8f822e77 R09: 1ffffffff1f045ce=20 R10: dffffc0000000000 R11: fffffbfff1f045cf R12: ffff8880b8740948=20 R13: dffffc0000000000 R14: ffff8880b863bb00 R15: 0000000000000001=20 FS: 00007f6e0f393880(0000) GS:ffff888125e1e000(0000) knlGS:0000000000000000=20 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033=20 CR2: 000055ec54628550 CR3: 000000007d7b8000 CR4: 00000000003526f0=20 Call Trace:=20 =20 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1043=20 __flush_tlb_multi arch/x86/include/asm/paravirt.h:91 [inline]=20 flush_tlb_multi arch/x86/mm/tlb.c:1382 [inline]=20 flush_tlb_mm_range+0x60a/0x1170 arch/x86/mm/tlb.c:1472=20 flush_tlb_page arch/x86/include/asm/tlbflush.h:324 [inline]=20 ptep_clear_flush+0x120/0x170 mm/pgtable-generic.c:103=20 wp_page_copy mm/memory.c:3785 [inline]=20 do_wp_page+0x1bb1/0x5810 mm/memory.c:4180=20 handle_pte_fault mm/memory.c:6289 [inline]=20 __handle_mm_fault mm/memory.c:6411 [inline]=20 handle_mm_fault+0x14c5/0x32b0 mm/memory.c:6580=20 do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336=20 handle_page_fault arch/x86/mm/fault.c:1476 [inline]=20 exc_page_fault+0x71/0xd0 arch/x86/mm/fault.c:1532=20 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618=20 RIP: 0033:0x7f6e0ecb5dfe=20 Code: 00 00 66 0f ef c0 41 0f 11 44 24 20 49 89 54 24 10 49 89 74 24 18 4c=20 89 66 10 4c 89 62 18 48 89 c2 48 83 ca 01 49 89 54 24 08 <49> 89 04 04 48=20 83 c4 10 5b 41 5c 41 5d c3 0f 1f 40 00 48 89 cf 48=20 RSP: 002b:00007fff1a84f050 EFLAGS: 00010206=20 RAX: 0000000000002a20 RBX: 0000000000000740 RCX: 000055ec54627e10=20 RDX: 0000000000002a21 RSI: 00007f6e0edf1b20 RDI: 000055ec54627e10=20 RBP: 00007f6e0edf1ac0 R08: 0000000000000740 R09: 0000000000000010=20 R10: 000055ec24e255e0 R11: 0000000000000004 R12: 000055ec54625b30=20 R13: 00007f6e0edf1ac0 R14: 0000000000000740 R15: 00007f6e0edf1ac0=20 =20 ---=20 If you want syzbot to run the reproducer, reply with:=20 #syz test: git://repo/address.git branch-or-commit-hash=20 If you attach or paste a git patch, syzbot will apply it before testing.