(2013/07/19 18:19), Yoshihiro YUNOMAE wrote:
> Add pipe_lock/unlock for splice_write to avoid oops by following competition:
>
> (1) An application gets fds of a trace buffer, virtio-serial, pipe.
> (2) The application does fork()
> (3) The processes execute splice_read(trace buffer) and
> splice_write(virtio-serial) via same pipe.
>
> <parent> <child>
> get fds of a trace buffer,
> virtio-serial, pipe
> |
> fork()----------create--------+
> | |
> splice(read) | ---+
> splice(write) | +-- no competition
> | splice(read) |
> | splice(write) ---+
> | |
> splice(read) |
> splice(write) splice(read) ------ competition
> | splice(write)
>
> Two processes share a pipe_inode_info structure. If the child execute
> splice(read) when the parent tries to execute splice(write), the
> structure can be broken. Existing virtio-serial driver does not get
> lock for the structure in splice_write, so this competition will induce
> oops.
>
> <oops messages>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
> IP: [<ffffffff811a6b5f>] splice_from_pipe_feed+0x6f/0x130
> PGD 7223e067 PUD 72391067 PMD 0
> Oops: 0000 [#1] SMP
> Modules linked in: lockd bnep bluetooth rfkill sunrpc ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_page_alloc snd_timer snd soundcore pcspkr virtio_net virtio_balloon i2c_piix4 i2c_core microcode uinput floppy
> CPU: 0 PID: 1072 Comm: compete-test Not tainted 3.10.0ws+ #55
> Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
> task: ffff880071b98000 ti: ffff88007b55e000 task.ti: ffff88007b55e000
> RIP: 0010:[<ffffffff811a6b5f>] [<ffffffff811a6b5f>] splice_from_pipe_feed+0x6f/0x130
> RSP: 0018:ffff88007b55fd78 EFLAGS: 00010287
> RAX: 0000000000000000 RBX: ffff88007b55fe20 RCX: 0000000000000000
> RDX: 0000000000001000 RSI: ffff88007a95ba30 RDI: ffff880036f9e6c0
> RBP: ffff88007b55fda8 R08: 00000000000006ec R09: ffff880077626708
> R10: 0000000000000003 R11: ffffffff8139ca59 R12: ffff88007a95ba30
> R13: 0000000000000000 R14: ffffffff8139dd00 R15: ffff880036f9e6c0
> FS: 00007f2e2e3a0740(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 0000000000000018 CR3: 0000000071bd1000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Stack:
> ffffffff8139ca59 ffff88007b55fe20 ffff880036f9e6c0 ffffffff8139dd00
> ffff8800776266c0 ffff880077626708 ffff88007b55fde8 ffffffff811a6e8e
> ffff88007b55fde8 ffffffff8139ca59 ffff880036f9e6c0 ffff88007b55fe20
> Call Trace:
> [<ffffffff8139ca59>] ? alloc_buf.isra.13+0x39/0xb0
> [<ffffffff8139dd00>] ? virtcons_restore+0x100/0x100
> [<ffffffff811a6e8e>] __splice_from_pipe+0x7e/0x90
> [<ffffffff8139ca59>] ? alloc_buf.isra.13+0x39/0xb0
> [<ffffffff8139d739>] port_fops_splice_write+0xe9/0x140
> [<ffffffff8127a3f4>] ? selinux_file_permission+0xc4/0x120
> [<ffffffff8139d650>] ? wait_port_writable+0x1b0/0x1b0
> [<ffffffff811a6fe0>] do_splice_from+0xa0/0x110
> [<ffffffff811a951f>] SyS_splice+0x5ff/0x6b0
> [<ffffffff8161facf>] tracesys+0xdd/0xe2
> Code: 49 8b 87 80 00 00 00 4c 8d 24 d0 8b 53 04 41 8b 44 24 0c 4d 8b 6c 24 10 39 d0 89 03 76 02 89 13 49 8b 44 24 10 4c 89 e6 4c 89 ff <ff> 50 18 85 c0 0f 85 aa 00 00 00 48 89 da 4c 89 e6 4c 89 ff 41
> RIP [<ffffffff811a6b5f>] splice_from_pipe_feed+0x6f/0x130
> RSP <ffff88007b55fd78>
> CR2: 0000000000000018
> ---[ end trace 24572beb7764de59 ]---
>
> V2: Fix a locking problem for error
Thanks, this looks good for me.
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
>
> Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@xxxxxxxxxxx>
> Cc: Amit Shah <amit.shah@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/char/virtio_console.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 8722656..8a15af3 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -936,16 +936,21 @@ static ssize_t port_fops_splice_write(struct pipe_inode_info *pipe,
> * pipe->nrbufs == 0 means there are no data to transfer,
> * so this returns just 0 for no data.
> */
> - if (!pipe->nrbufs)
> - return 0;
> + pipe_lock(pipe);
> + if (!pipe->nrbufs) {
> + ret = 0;
> + goto error_out;
> + }
>
> ret = wait_port_writable(port, filp->f_flags & O_NONBLOCK);
> if (ret < 0)
> - return ret;
> + goto error_out;
>
> buf = alloc_buf(port->out_vq, 0, pipe->nrbufs);
> - if (!buf)
> - return -ENOMEM;
> + if (!buf) {
> + ret = -ENOMEM;
> + goto error_out;
> + }
>
> sgl.n = 0;
> sgl.len = 0;
> @@ -953,12 +958,17 @@ static ssize_t port_fops_splice_write(struct pipe_inode_info *pipe,
> sgl.sg = buf->sg;
> sg_init_table(sgl.sg, sgl.size);
> ret = __splice_from_pipe(pipe, &sd, pipe_to_sg);
> + pipe_unlock(pipe);
> if (likely(ret > 0))
> ret = __send_to_port(port, buf->sg, sgl.n, sgl.len, buf, true);
>
> if (unlikely(ret <= 0))
> free_buf(buf, true);
> return ret;
> +
> +error_out:
> + pipe_unlock(pipe);
> + return ret;
> }
>
> static unsigned int port_fops_poll(struct file *filp, poll_table *wait)
>
>
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@xxxxxxxxxxx
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