Comment 0 for bug 1772031

kernel 4.13.0-41-generic is missing commit a90bcb86ae70:

Author: Petar Penkov <email address hidden>
Date: Tue Aug 29 11:20:32 2017 -0700

    iov_iter: fix page_copy_sane for compound pages

    Issue is that if the data crosses a page boundary inside a compound
    page, this check will incorrectly trigger a WARN_ON.

    To fix this, compute the order using the head of the compound page and
    adjust the offset to be relative to that head.

    Fixes: 72e809ed81ed ("iov_iter: sanity checks for copy to/from page
    primitives")

    Signed-off-by: Petar Penkov <email address hidden>
    CC: Al Viro <email address hidden>
    CC: Eric Dumazet <email address hidden>
    Signed-off-by: Al Viro <email address hidden>

Commit 72e809ed81ed is in kernel 4.13.0-41-generic.
As a result, when receiving large UDP packages with a small MTU we get backtraces like:

[ 361.260969] ------------[ cut here ]------------
[ 361.260974] WARNING: CPU: 4 PID: 2541 at /build/linux-hwe-v6kHHF/linux-hwe-4.13.0/lib/iov_iter.c:693 copy_page_to_iter+0x194/0x2d0
[ 361.260975] Modules linked in: cmdlinepart sfc(OE) hwmon_vid crc32_generic mii rpcsec_gss_krb5 auth_rpcgss nfsv4 nfs lockd grace fscache 8021q garp mrp stp llc intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm i]
[ 361.261002] CPU: 4 PID: 2541 Comm: udp_recv Tainted: G OE 4.13.0-39-generic #44~16.04.1-Ubuntu
[ 361.261003] Hardware name: Dell Inc. PowerEdge R220/05Y15N, BIOS 1.4.0 10/23/2014
[ 361.261004] task: ffff91630b2bae80 task.stack: ffffbb19c2bfc000
[ 361.261005] RIP: 0010:copy_page_to_iter+0x194/0x2d0
[ 361.261006] RSP: 0018:ffffbb19c2bffc60 EFLAGS: 00010202
[ 361.261007] RAX: 0000000000001000 RBX: 00000000000000df RCX: 0017ffffc0000000
[ 361.261008] RDX: 00000000000000df RSI: 0000000000000f8e RDI: fffff666895279c0
[ 361.261009] RBP: ffffbb19c2bffca0 R08: 000000000000106d R09: 0000000000001024
[ 361.261009] R10: 0000000000000000 R11: ffff91630ccc9b00 R12: ffff91630d27a300
[ 361.261010] R13: ffffbb19c2bffde0 R14: 00000000000000df R15: 0000000000000175
[ 361.261011] FS: 00007fb8e7649700(0000) GS:ffff91631fd00000(0000) knlGS:0000000000000000
[ 361.261012] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 361.261013] CR2: 000014588da85624 CR3: 000000024bad2002 CR4: 00000000001606e0
[ 361.261013] Call Trace:
[ 361.261017] ? proto_init_net+0x40/0x40
[ 361.261019] skb_copy_datagram_iter+0x171/0x270
[ 361.261022] udp_recvmsg+0x108/0x490
[ 361.261024] inet_recvmsg+0x51/0xc0
[ 361.261026] sock_recvmsg+0x43/0x50
[ 361.261028] sock_read_iter+0x90/0xe0
[ 361.261030] new_sync_read+0xe2/0x130
[ 361.261032] __vfs_read+0x29/0x40
[ 361.261033] vfs_read+0x93/0x130
[ 361.261034] SyS_read+0x55/0xc0
[ 361.261037] entry_SYSCALL_64_fastpath+0x24/0xab
[ 361.261038] RIP: 0033:0x7fb8e7160260
[ 361.261039] RSP: 002b:00007ffed9dd9e38 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[ 361.261040] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb8e7160260
[ 361.261041] RDX: 000000000000ffe3 RSI: 00005622ad02f0a0 RDI: 0000000000000003
[ 361.261041] RBP: 00007ffed9dd9e70 R08: 0000000000000000 R09: 0000000000000011
[ 361.261042] R10: 0000000000000000 R11: 0000000000000246 R12: 00005622ace2e800
[ 361.261043] R13: 00007ffed9dd9f50 R14: 0000000000000000 R15: 0000000000000000
[ 361.261044] Code: de 4c 89 e7 e8 be fa ff ff 41 83 af a0 12 00 00 01 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f 5d c3 8b 4f 6c 48 d3 e0 e9 9d fe ff ff <0f> ff 48 83 c4 18 31 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 49 83
[ 361.261064] ---[ end trace c0b23bf37be9874d ]---

This is a request to pull in commit a90bcb86ae70.

# lsb_release -rd
Description: Ubuntu 17.10
Release: 17.10
# uname -a
Linux c6320f 4.13.0-41-generic #46-Ubuntu SMP Wed May 2 13:38:30 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
# cat /proc/version_signature
Ubuntu 4.13.0-41.46-generic 4.13.16