Messages in this thread | | | From | Dmitry Vyukov <> | Date | Thu, 2 Feb 2017 19:03:41 +0100 | Subject | Re: tty: panic in tty_ldisc_restore |
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On Thu, Feb 2, 2017 at 6:55 PM, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > On Thu, Feb 02, 2017 at 06:48:48PM +0100, Dmitry Vyukov wrote: >> Hello, >> >> Syzkaller fuzzer started crashing kernel with the following panics: >> >> Kernel panic - not syncing: Couldn't open N_TTY ldisc for ircomm0 --- error -12. >> CPU: 0 PID: 5637 Comm: syz-executor3 Not tainted 4.9.0 #6 >> Hardware name: Google Google Compute Engine/Google Compute Engine, >> BIOS Google 01/01/2011 >> ffff8801d4ba7a18 ffffffff8234d0df ffffffff00000000 1ffff1003a974ed6 >> ffffed003a974ece 0000000041b58ab3 ffffffff84b38180 ffffffff8234cdf1 >> 0000000000000000 0000000000000000 ffff8801d4ba76a8 00000000dabb4fad >> Call Trace: >> [<ffffffff8234d0df>] __dump_stack lib/dump_stack.c:15 [inline] >> [<ffffffff8234d0df>] dump_stack+0x2ee/0x3ef lib/dump_stack.c:51 >> [<ffffffff818280d4>] panic+0x1fb/0x412 kernel/panic.c:179 >> [<ffffffff826bb0d4>] tty_ldisc_restore drivers/tty/tty_ldisc.c:520 [inline] >> [<ffffffff826bb0d4>] tty_set_ldisc+0x704/0x8b0 drivers/tty/tty_ldisc.c:579 >> [<ffffffff826a3a93>] tiocsetd drivers/tty/tty_io.c:2667 [inline] >> [<ffffffff826a3a93>] tty_ioctl+0xc63/0x2370 drivers/tty/tty_io.c:2924 >> [<ffffffff81a7a22f>] vfs_ioctl fs/ioctl.c:43 [inline] >> [<ffffffff81a7a22f>] do_vfs_ioctl+0x1bf/0x1630 fs/ioctl.c:679 >> [<ffffffff81a7b72f>] SYSC_ioctl fs/ioctl.c:694 [inline] >> [<ffffffff81a7b72f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 >> [<ffffffff84377941>] entry_SYSCALL_64_fastpath+0x1f/0xc2 >> >> Kernel panic - not syncing: Couldn't open N_TTY ldisc for ptm2 --- error -12. >> CPU: 0 PID: 7844 Comm: syz-executor0 Not tainted 4.9.0 #6 >> Hardware name: Google Google Compute Engine/Google Compute Engine, >> BIOS Google 01/01/2011 >> ffff8801c3307a18 ffffffff8234d0df ffffffff00000000 1ffff10038660ed6 >> ffffed0038660ece 0000000041b58ab3 ffffffff84b38180 ffffffff8234cdf1 >> 0000000000000000 0000000000000000 ffff8801c33076a8 00000000dabb4fad >> Call Trace: >> [<ffffffff8234d0df>] __dump_stack lib/dump_stack.c:15 [inline] >> [<ffffffff8234d0df>] dump_stack+0x2ee/0x3ef lib/dump_stack.c:51 >> [<ffffffff818280d4>] panic+0x1fb/0x412 kernel/panic.c:179 >> [<ffffffff826bb0d4>] tty_ldisc_restore drivers/tty/tty_ldisc.c:520 [inline] >> [<ffffffff826bb0d4>] tty_set_ldisc+0x704/0x8b0 drivers/tty/tty_ldisc.c:579 >> [<ffffffff826a3a93>] tiocsetd drivers/tty/tty_io.c:2667 [inline] >> [<ffffffff826a3a93>] tty_ioctl+0xc63/0x2370 drivers/tty/tty_io.c:2924 >> [<ffffffff81a7a22f>] vfs_ioctl fs/ioctl.c:43 [inline] >> [<ffffffff81a7a22f>] do_vfs_ioctl+0x1bf/0x1630 fs/ioctl.c:679 >> [<ffffffff81a7b72f>] SYSC_ioctl fs/ioctl.c:694 [inline] >> [<ffffffff81a7b72f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 >> [<ffffffff84377941>] entry_SYSCALL_64_fastpath+0x1f/0xc2 >> >> >> In all cases there is a vmalloc failure right before that: >> >> syz-executor4: vmalloc: allocation failure, allocated 0 of 16384 >> bytes, mode:0x14000c2(GFP_KERNEL|__GFP_HIGHMEM), nodemask=(null) >> syz-executor4 cpuset=/ mems_allowed=0 >> CPU: 1 PID: 4852 Comm: syz-executor4 Not tainted 4.9.0 #6 >> Hardware name: Google Google Compute Engine/Google Compute Engine, >> BIOS Google 01/01/2011 >> ffff8801c41df898 ffffffff8234d0df ffffffff00000001 1ffff1003883bea6 >> ffffed003883be9e 0000000041b58ab3 ffffffff84b38180 ffffffff8234cdf1 >> 0000000000000282 ffffffff84fd53c0 ffff8801dae65b38 ffff8801c41df4d0 >> Call Trace: >> [< inline >] __dump_stack lib/dump_stack.c:15 >> [<ffffffff8234d0df>] dump_stack+0x2ee/0x3ef lib/dump_stack.c:51 >> [<ffffffff8186530f>] warn_alloc+0x21f/0x360 >> [<ffffffff819792c9>] __vmalloc_node_range+0x4e9/0x770 >> [< inline >] __vmalloc_node mm/vmalloc.c:1749 >> [< inline >] __vmalloc_node_flags mm/vmalloc.c:1763 >> [<ffffffff8197961b>] vmalloc+0x5b/0x70 mm/vmalloc.c:1778 >> [<ffffffff826ad77b>] n_tty_open+0x1b/0x470 drivers/tty/n_tty.c:1883 >> [<ffffffff826ba973>] tty_ldisc_open.isra.3+0x73/0xd0 >> drivers/tty/tty_ldisc.c:463 >> [< inline >] tty_ldisc_restore drivers/tty/tty_ldisc.c:510 >> [<ffffffff826bafb4>] tty_set_ldisc+0x5e4/0x8b0 drivers/tty/tty_ldisc.c:579 >> [< inline >] tiocsetd drivers/tty/tty_io.c:2667 >> [<ffffffff826a3a93>] tty_ioctl+0xc63/0x2370 drivers/tty/tty_io.c:2924 >> [<ffffffff81a7a22f>] do_vfs_ioctl+0x1bf/0x1630 >> [< inline >] SYSC_ioctl fs/ioctl.c:698 >> [<ffffffff81a7b72f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689 >> [<ffffffff84377941>] entry_SYSCALL_64_fastpath+0x1f/0xc2 >> arch/x86/entry/entry_64.S:204 >> >> >> I've found that it's even documented in the source code, but it does >> not look like a good failure mode for allocation failure: >> >> static int n_tty_open(struct tty_struct *tty) >> { >> struct n_tty_data *ldata; >> >> /* Currently a malloc failure here can panic */ >> ldata = vmalloc(sizeof(*ldata)); > > How are you running out of vmalloc() memory?
I don't know exactly. But it does not seem to represent a problem for the fuzzer. Is it meant to be very hard to do?
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