Messages in this thread Patch in this message | | | From | "Fabio M. De Francesco" <> | Subject | Re: [syzbot] BUG: sleeping function called from invalid context in __might_resched | Date | Tue, 16 Nov 2021 08:57:49 +0100 |
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On Saturday, November 13, 2021 9:13:24 PM CET syzbot wrote: > syzbot has found a reproducer for the following issue on: > > HEAD commit: f2e19fd15bd7 Add linux-next specific files for 20211112 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=15def132b00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=ba9c83199208e103 > dashboard link: https://syzkaller.appspot.com/bug? extid=5f47a8cea6a12b77a876 > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12bdb2c9b00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=109194aab00000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+5f47a8cea6a12b77a876@syzkaller.appspotmail.com > > BUG: sleeping function called from invalid context at kernel/printk/ printk.c:2525 > in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 6529, name: syz- executor925 > preempt_count: 1, expected: 0 > RCU nest depth: 0, expected: 0 > 3 locks held by syz-executor925/6529: > #0: ffff888018d79098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:252 > #1: ffff888018d79468 (&tty->flow.lock){....}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:379 [inline] > #1: ffff888018d79468 (&tty->flow.lock){....}-{2:2}, at: n_tty_ioctl_helper+0xb6/0x2d0 drivers/tty/tty_ioctl.c:877 > #2: ffff888018d79098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:273 > irq event stamp: 16252 > hardirqs last enabled at (16251): [<ffffffff8952dbc0>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline] > hardirqs last enabled at (16251): [<ffffffff8952dbc0>] _raw_spin_unlock_irqrestore+0x50/0x70 kernel/locking/spinlock.c:194 > hardirqs last disabled at (16252): [<ffffffff8952d921>] __raw_spin_lock_irq include/linux/spinlock_api_smp.h:117 [inline] > hardirqs last disabled at (16252): [<ffffffff8952d921>] _raw_spin_lock_irq+0x41/0x50 kernel/locking/spinlock.c:170 > softirqs last enabled at (14452): [<ffffffff812bc45c>] fpu_reset_fpregs arch/x86/kernel/fpu/core.c:601 [inline] > softirqs last enabled at (14452): [<ffffffff812bc45c>] fpu_flush_thread+0x23c/0x390 arch/x86/kernel/fpu/core.c:647 > softirqs last disabled at (14450): [<ffffffff812bc3eb>] fpstate_reset arch/ x86/kernel/fpu/core.c:452 [inline] > softirqs last disabled at (14450): [<ffffffff812bc3eb>] fpu_flush_thread+0x1cb/0x390 arch/x86/kernel/fpu/core.c:646 > Preemption disabled at: > [<0000000000000000>] 0x0 > CPU: 0 PID: 6529 Comm: syz-executor925 Not tainted 5.15.0-next-20211112- syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > __might_resched.cold+0x222/0x26b kernel/sched/core.c:9554 > console_lock+0x17/0x80 kernel/printk/printk.c:2525 > do_con_write+0x10f/0x1e40 drivers/tty/vt/vt.c:2908 > con_write+0x21/0x40 drivers/tty/vt/vt.c:3295 > n_hdlc_send_frames+0x24b/0x490 drivers/tty/n_hdlc.c:290 > tty_wakeup+0xe1/0x120 drivers/tty/tty_io.c:534 > __start_tty drivers/tty/tty_io.c:806 [inline] > __start_tty+0xfb/0x130 drivers/tty/tty_io.c:799 > n_tty_ioctl_helper+0x299/0x2d0 drivers/tty/tty_ioctl.c:880 > n_hdlc_tty_ioctl+0xd2/0x340 drivers/tty/n_hdlc.c:633 > tty_ioctl+0xc69/0x1670 drivers/tty/tty_io.c:2814 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:874 [inline] > __se_sys_ioctl fs/ioctl.c:860 [inline] > __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x7f16c8522349 > Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007fff6ccb8b98 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f16c8522349 > RDX: 0000000000000001 RSI: 000000000000540a RDI: 0000000000000005 > RBP: 00007f16c84e61d0 R08: 0000000000000000 R09: 0000000000000000 > R10: 00000000000
I think that thanks to Marco Elver we have a solution for this issue.
However I'd propose a transformation on Marco's solution based on one of the De Morgan's laws: !(A && B) <=> !A || !B.
I think that this is more readable and comprehensible.
Therefore, if I'm not wrong, Marco's "!preemptible()", that is "if (! (preempt_count() == 0 && !irqs_disabled())", might be rewritten to an easier to understand "if (preempt_count() || irqs_disabled())".
Am I wrong? Let's test it...
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
-- Fabio M. De Francesco
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 7359c3e80d63..a0c6d29eb2a6 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -2902,7 +2902,7 @@ static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int co struct vt_notifier_param param; bool rescan; - if (in_interrupt()) + if (preempt_count() || irqs_disabled()) return count; console_lock(); | |