net: qrtr: Fix memory leak in qrtr_tun_open

If qrtr_endpoint_register() failed, tun is leaked.
Fix this, by freeing tun in error path.

syzbot report:
BUG: memory leak
unreferenced object 0xffff88811848d680 (size 64):
comm "syz-executor684", pid 10171, jiffies 4294951561 (age 26.070s)
hex dump (first 32 bytes):
80 dd 0a 84 ff ff ff ff 00 00 00 00 00 00 00 00 ................
90 d6 48 18 81 88 ff ff 90 d6 48 18 81 88 ff ff ..H.......H.....
backtrace:
[<0000000018992a50>] kmalloc include/linux/slab.h:552 [inline]
[<0000000018992a50>] kzalloc include/linux/slab.h:682 [inline]
[<0000000018992a50>] qrtr_tun_open+0x22/0x90 net/qrtr/tun.c:35
[<0000000003a453ef>] misc_open+0x19c/0x1e0 drivers/char/misc.c:141
[<00000000dec38ac8>] chrdev_open+0x10d/0x340 fs/char_dev.c:414
[<0000000079094996>] do_dentry_open+0x1e6/0x620 fs/open.c:817
[<000000004096d290>] do_open fs/namei.c:3252 [inline]
[<000000004096d290>] path_openat+0x74a/0x1b00 fs/namei.c:3369
[<00000000b8e64241>] do_filp_open+0xa0/0x190 fs/namei.c:3396
[<00000000a3299422>] do_sys_openat2+0xed/0x230 fs/open.c:1172
[<000000002c1bdcef>] do_sys_open fs/open.c:1188 [inline]
[<000000002c1bdcef>] __do_sys_openat fs/open.c:1204 [inline]
[<000000002c1bdcef>] __se_sys_openat fs/open.c:1199 [inline]
[<000000002c1bdcef>] __x64_sys_openat+0x7f/0xe0 fs/open.c:1199
[<00000000f3a5728f>] do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
[<000000004b38b7ec>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 28fb4e59a47d ("net: qrtr: Expose tunneling endpoint to user space")
Reported-by: syzbot+5d6e4af21385f5cfc56a@syzkaller.appspotmail.com
Signed-off-by: Takeshi Misawa <jeliantsurux@gmail.com>
Link: https://lore.kernel.org/r/20210221234427.GA2140@DESKTOP
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/qrtr: restrict user-controlled length in qrtr_tun_write_iter()

syzbot found WARNING in qrtr_tun_write_iter [1] when write_iter length
exceeds KMALLOC_MAX_SIZE causing order >= MAX_ORDER condition.

Additionally, there is no check for 0 length write.

[1]
WARNING: mm/page_alloc.c:5011
[..]
Call Trace:
alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2267
alloc_pages include/linux/gfp.h:547 [inline]
kmalloc_order+0x2e/0xb0 mm/slab_common.c:837
kmalloc_order_trace+0x14/0x120 mm/slab_common.c:853
kmalloc include/linux/slab.h:557 [inline]
kzalloc include/linux/slab.h:682 [inline]
qrtr_tun_write_iter+0x8a/0x180 net/qrtr/tun.c:83
call_write_iter include/linux/fs.h:1901 [inline]

Reported-by: syzbot+c2a7e5c5211605a90865@syzkaller.appspotmail.com
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Link: https://lore.kernel.org/r/20210202092059.1361381-1-snovitoll@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net: qrtr: Simplify 'qrtr_tun_release()'

Use 'skb_queue_purge()' instead of re-implementing it.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: qrtr: fix memort leak in qrtr_tun_write_iter

In qrtr_tun_write_iter the allocated kbuf should be release in case of
error or success return.

v2 Update: Thanks to David Miller for pointing out the release on success
path as well.

Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: qrtr: Expose tunneling endpoint to user space

This implements a misc character device named "qrtr-tun" for the purpose
of allowing user space applications to implement endpoints in the qrtr
network.

This allows more advanced (and dynamic) testing of the qrtr code as well
as opens up the ability of tunneling qrtr over a network or USB link.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>