mainlining shenanigans
e7c87bd6cc
Syzkaller was able to construct a packet of negative length by
redirecting from bpf_prog_test_run_skb with BPF_PROG_TYPE_LWT_XMIT:
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:345 [inline]
BUG: KASAN: slab-out-of-bounds in skb_copy_from_linear_data include/linux/skbuff.h:3421 [inline]
BUG: KASAN: slab-out-of-bounds in __pskb_copy_fclone+0x2dd/0xeb0 net/core/skbuff.c:1395
Read of size 4294967282 at addr ffff8801d798009c by task syz-executor2/12942
kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
check_memory_region_inline mm/kasan/kasan.c:260 [inline]
check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
memcpy+0x23/0x50 mm/kasan/kasan.c:302
memcpy include/linux/string.h:345 [inline]
skb_copy_from_linear_data include/linux/skbuff.h:3421 [inline]
__pskb_copy_fclone+0x2dd/0xeb0 net/core/skbuff.c:1395
__pskb_copy include/linux/skbuff.h:1053 [inline]
pskb_copy include/linux/skbuff.h:2904 [inline]
skb_realloc_headroom+0xe7/0x120 net/core/skbuff.c:1539
ipip6_tunnel_xmit net/ipv6/sit.c:965 [inline]
sit_tunnel_xmit+0xe1b/0x30d0 net/ipv6/sit.c:1029
__netdev_start_xmit include/linux/netdevice.h:4325 [inline]
netdev_start_xmit include/linux/netdevice.h:4334 [inline]
xmit_one net/core/dev.c:3219 [inline]
dev_hard_start_xmit+0x295/0xc90 net/core/dev.c:3235
__dev_queue_xmit+0x2f0d/0x3950 net/core/dev.c:3805
dev_queue_xmit+0x17/0x20 net/core/dev.c:3838
__bpf_tx_skb net/core/filter.c:2016 [inline]
__bpf_redirect_common net/core/filter.c:2054 [inline]
__bpf_redirect+0x5cf/0xb20 net/core/filter.c:2061
____bpf_clone_redirect net/core/filter.c:2094 [inline]
bpf_clone_redirect+0x2f6/0x490 net/core/filter.c:2066
bpf_prog_41f2bcae09cd4ac3+0xb25/0x1000
The generated test constructs a packet with mac header, network
header, skb->data pointing to network header and skb->len 0.
Redirecting to a sit0 through __bpf_redirect_no_mac pulls the
mac length, even though skb->data already is at skb->network_header.
bpf_prog_test_run_skb has already pulled it as LWT_XMIT !is_l2.
Update the offset calculation to pull only if skb->data differs
from skb->network_header, which is not true in this case.
The test itself can be run only from commit
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.