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KASAN: slab-out-of-bounds Read in bpf_skb_change_proto

Status: fixed on 2018/07/09 18:05
Subsystems: bpf net
[Documentation on labels]
Reported-by: syzbot+d2d729bdde65dee3eae6@syzkaller.appspotmail.com
Fix commit: 58990d1ff3f7 bpf: reject passing modified ctx to helper functions
First crash: 2169d, last: 2169d
Discussions (1)
Title Replies (including bot) Last reply
KASAN: slab-out-of-bounds Read in bpf_skb_change_proto 3 (4) 2018/06/11 10:31
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 KASAN: slab-out-of-bounds Read in bpf_skb_change_proto C done 2 1596d 1743d 1/1 fixed on 2020/02/05 13:33
android-414 KASAN: slab-out-of-bounds Read in bpf_skb_change_proto C 11 1643d 1863d 0/1 public: reported C repro on 2019/04/12 00:01

Sample crash report:
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
==================================================================
BUG: KASAN: slab-out-of-bounds in bpf_skb_proto_xlat net/core/filter.c:2637 [inline]
BUG: KASAN: slab-out-of-bounds in ____bpf_skb_change_proto net/core/filter.c:2675 [inline]
BUG: KASAN: slab-out-of-bounds in bpf_skb_change_proto+0xe37/0x1300 net/core/filter.c:2650
Read of size 2 at addr ffff8801b04646c0 by task syz-executor241/4519

CPU: 0 PID: 4519 Comm: syz-executor241 Not tainted 4.17.0+ #93
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1b9/0x294 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:431
 bpf_skb_proto_xlat net/core/filter.c:2637 [inline]
 ____bpf_skb_change_proto net/core/filter.c:2675 [inline]
 bpf_skb_change_proto+0xe37/0x1300 net/core/filter.c:2650

Allocated by task 0:
(stack is not available)

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801b04646c0
 which belongs to the cache skbuff_head_cache of size 232
The buggy address is located 0 bytes inside of
 232-byte region [ffff8801b04646c0, ffff8801b04647a8)
The buggy address belongs to the page:
page:ffffea0006c11900 count:1 mapcount:0 mapping:ffff8801d9a0d080 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0006c49388 ffffea0006ae5c48 ffff8801d9a0d080
raw: 0000000000000000 ffff8801b0464080 000000010000000c 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801b0464580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801b0464600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801b0464680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                           ^
 ffff8801b0464700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801b0464780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/06/10 06:43 upstream a16afaf7928b 866118af .config console log report syz C ci-upstream-kasan-gce-root
2018/06/09 17:44 bpf-next 75d4e704fa8d 866118af .config console log report syz C ci-upstream-bpf-next-kasan-gce
* Struck through repros no longer work on HEAD.