From 98c9710e0aa2b939423605488b5817f27118ce40 Mon Sep 17 00:00:00 2001 From: Yoshihiro YUNOMAE Date: Tue, 23 Jul 2013 11:30:49 +0930 Subject: [PATCH] virtio/console: Add pipe_lock/unlock for splice_write commit 2b4fbf029dff5a28d9bf646346dea891ec43398a upstream. 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. 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. BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 IP: [] 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:[] [] 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: [] ? alloc_buf.isra.13+0x39/0xb0 [] ? virtcons_restore+0x100/0x100 [] __splice_from_pipe+0x7e/0x90 [] ? alloc_buf.isra.13+0x39/0xb0 [] port_fops_splice_write+0xe9/0x140 [] ? selinux_file_permission+0xc4/0x120 [] ? wait_port_writable+0x1b0/0x1b0 [] do_splice_from+0xa0/0x110 [] SyS_splice+0x5ff/0x6b0 [] 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 50 18 85 c0 0f 85 aa 00 00 00 48 89 da 4c 89 e6 4c 89 ff 41 RIP [] splice_from_pipe_feed+0x6f/0x130 RSP CR2: 0000000000000018 ---[ end trace 24572beb7764de59 ]--- V2: Fix a locking problem for error V3: Add Reviewed-by lines and stable@ line in sign-off area Signed-off-by: Yoshihiro YUNOMAE Reviewed-by: Amit Shah Reviewed-by: Masami Hiramatsu Cc: Amit Shah Cc: Arnd Bergmann Signed-off-by: Rusty Russell Signed-off-by: Greg Kroah-Hartman --- 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) -- 2.7.4