Re: [PATCH] net/qrtr: restrict user-controlled length in qrtr_tun_write_iter()

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Tue,  2 Feb 2021 15:20:59 +0600 you wrote:

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]

[...]

Here is the summary with links:
  - net/qrtr: restrict user-controlled length in qrtr_tun_write_iter()
    https://git.kernel.org/netdev/net/c/2a80c1581237

You are awesome, thank you!
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