@@ -942,16 +942,21 @@ 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;
@@ -959,12 +964,17 @@ 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)
This is a note to let you know that I have just added a patch titled virtio/console: Add pipe_lock/unlock for splice_write to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue This patch is scheduled to be released in version 3.8.13.7. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From c414f0cf0d9bd0b4c3169e280c639623d676f54c Mon Sep 17 00:00:00 2001 From: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com> Date: Tue, 23 Jul 2013 11:30:49 +0930 Subject: 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. <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 V3: Add Reviewed-by lines and stable@ line in sign-off area Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com> Reviewed-by: Amit Shah <amit.shah@redhat.com> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Amit Shah <amit.shah@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- drivers/char/virtio_console.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) -- 1.8.1.2