Re: [syzbot] BUG: unable to handle kernel NULL pointer dereference in tiocsti

[Jiri Slaby]

#syz dup: BUG: unable to handle kernel NULL pointer dereference in 
gsmld_receive_buf

On 24. 08. 22, 18:35, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    1c23f9e627a7 Linux 6.0-rc2
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=17eefdcb080000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3045c937aad027f7
> dashboard link: https://syzkaller.appspot.com/bug?extid=032314e8d7de2bdb97f7
> compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1190eb6b080000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16a1e50d080000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+032314e8d7de2bdb97f7@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> Mem abort info:
>    ESR = 0x0000000086000006
>    EC = 0x21: IABT (current EL), IL = 32 bits
>    SET = 0, FnV = 0
>    EA = 0, S1PTW = 0
>    FSC = 0x06: level 2 translation fault
> user pgtable: 4k pages, 48-bit VAs, pgdp=000000010b28b000
> [0000000000000000] pgd=080000010b411003, p4d=080000010b411003, pud=080000010b47b003, pmd=0000000000000000
> Internal error: Oops: 86000006 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 1 PID: 3028 Comm: syz-executor908 Not tainted 6.0.0-rc2-syzkaller-16440-g1c23f9e627a7 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/20/2022
> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : 0x0
> lr : gsmld_receive_buf+0x140/0x214 drivers/tty/n_gsm.c:2861
> sp : ffff80000ffe3cb0
> x29: ffff80000ffe3cc0 x28: 0000000000000000 x27: 0000000000000000
> x26: 0000000000000000 x25: 0000000000000000 x24: ffff80000d937000
> x23: ffff80000d681e40 x22: ffff0000cb2dc000 x21: ffff80000ffe3d21
> x20: ffff80000c205988 x19: ffff80000ffe3d24 x18: 00000000000000c0
> x17: ffff80000dd7a698 x16: 0000000000000000 x15: 0000000000000000
> x14: 0000000000000000 x13: 0000000000000004 x12: ffff80000d681e78
> x11: ff808000098e7e04 x10: 0000000000000000 x9 : ffff8000098e7e04
> x8 : 0000000000000000 x7 : ffff8000098dcea4 x6 : 0000000000000000
> x5 : ffff80000e087890 x4 : 0000000000000002 x3 : 0000000000000001
> x2 : ffff80000ffe3d20 x1 : 0000000000000000 x0 : ffff0000cb2dc000
> Call trace:
>   0x0
>   tiocsti+0x168/0x1c4 drivers/tty/tty_io.c:2293
>   tty_ioctl+0x284/0x9f4 drivers/tty/tty_io.c:2692
>   vfs_ioctl fs/ioctl.c:51 [inline]
>   __do_sys_ioctl fs/ioctl.c:870 [inline]
>   __se_sys_ioctl fs/ioctl.c:856 [inline]
>   __arm64_sys_ioctl+0xd0/0x140 fs/ioctl.c:856
>   __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
>   invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
>   el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
>   do_el0_svc+0x48/0x154 arch/arm64/kernel/syscall.c:206
>   el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:624
>   el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:642
>   el0t_64_sync+0x18c/0x190
> Code: bad PC value
> ---[ end trace 0000000000000000 ]---
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
>
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> syzbot can test patches for this issue, for details see:
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