On 11/12/20 9:37 PM, Matt Mullins wrote:
On Wed, Nov 11, 2020 at 03:57:50PM +0100, Dmitry Vyukov wrote:
On Mon, Nov 2, 2020 at 12:54 PM syzbot
<syzbot+d29e58bb557324e55e5e@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Hello,
syzbot found the following issue on:
HEAD commit: 080b6f40 bpf: Don't rely on GCC __attribute__((optimize)) ..
git tree: bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=1089d37c500000
kernel config: https://syzkaller.appspot.com/x/.config?x=58a4ca757d776bfe
dashboard link: https://syzkaller.appspot.com/bug?extid=d29e58bb557324e55e5e
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10f4b032500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1371a47c500000
The issue was bisected to:
commit 9df1c28bb75217b244257152ab7d788bb2a386d0
Author: Matt Mullins <mmullins@xxxxxx>
Date: Fri Apr 26 18:49:47 2019 +0000
bpf: add writable context for raw tracepoints
We have a number of kernel memory corruptions related to bpf_trace_run now:
https://groups.google.com/g/syzkaller-bugs/search?q=kernel/trace/bpf_trace.c
Can raw tracepoints "legally" corrupt kernel memory (a-la /dev/kmem)?
Or they shouldn't?
Looking at the description of Matt's commit, it seems that corruptions
should not be possible (bounded buffer, checked size, etc). Then it
means it's a real kernel bug?
This bug doesn't seem to be related to the writability of the
tracepoint; it bisected to that commit simply because it used
BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE for the reproducer and it EINVAL's
before that program type was introduced. The BPF program it loads is
pretty much a no-op.
The problem here is a kmalloc failure injection into
tracepoint_probe_unregister, but the error is ignored -- so the bpf
program is freed even though the tracepoint is never unregistered.
I have a first pass at a patch to pipe through the error code, but it's
pretty ugly. It's also called from the file_operations ->release(), for
Maybe you can still post the patch, so people can review and make
suggestions which may lead to a *better* solution.
which errors are solidly ignored in __fput(), so I'm not sure what the
best way to handle ENOMEM is...
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12b6c4da500000
final oops: https://syzkaller.appspot.com/x/report.txt?x=11b6c4da500000
console output: https://syzkaller.appspot.com/x/log.txt?x=16b6c4da500000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d29e58bb557324e55e5e@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 9df1c28bb752 ("bpf: add writable context for raw tracepoints")
==================================================================
BUG: KASAN: vmalloc-out-of-bounds in __bpf_trace_run kernel/trace/bpf_trace.c:2045 [inline]
BUG: KASAN: vmalloc-out-of-bounds in bpf_trace_run3+0x3e0/0x3f0 kernel/trace/bpf_trace.c:2083
Read of size 8 at addr ffffc90000e6c030 by task kworker/0:3/3754
CPU: 0 PID: 3754 Comm: kworker/0:3 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: 0x0 (events)
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x107/0x163 lib/dump_stack.c:118
print_address_description.constprop.0.cold+0x5/0x4c8 mm/kasan/report.c:385
__kasan_report mm/kasan/report.c:545 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
__bpf_trace_run kernel/trace/bpf_trace.c:2045 [inline]
bpf_trace_run3+0x3e0/0x3f0 kernel/trace/bpf_trace.c:2083
__bpf_trace_sched_switch+0xdc/0x120 include/trace/events/sched.h:138
__traceiter_sched_switch+0x64/0xb0 include/trace/events/sched.h:138
trace_sched_switch include/trace/events/sched.h:138 [inline]
__schedule+0xeb8/0x2130 kernel/sched/core.c:4520
schedule+0xcf/0x270 kernel/sched/core.c:4601
worker_thread+0x14c/0x1120 kernel/workqueue.c:2439
kthread+0x3af/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
Memory state around the buggy address:
ffffc90000e6bf00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffffc90000e6bf80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffffc90000e6c000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
^
ffffc90000e6c080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffffc90000e6c100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================
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