Messages in this thread Patch in this message | | | Subject | [PATCH 2/2] [BUGFIX] virtio/console: Add pipe_lock/unlock for splice_write | From | Yoshihiro YUNOMAE <> | Date | Fri, 19 Jul 2013 08:19:32 +0900 |
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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 ]---
Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com> Cc: Amit Shah <amit.shah@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/char/virtio_console.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 8722656..4a28e4c 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -936,6 +936,7 @@ 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. */ + pipe_lock(pipe); if (!pipe->nrbufs) return 0; @@ -953,6 +954,7 @@ 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);
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