* [syzbot] KASAN: use-after-free Read in put_pmu_ctx
@ 2022-12-19 8:04 syzbot
2022-12-19 14:40 ` Peter Zijlstra
2022-12-20 8:25 ` Peter Zijlstra
0 siblings, 2 replies; 15+ messages in thread
From: syzbot @ 2022-12-19 8:04 UTC (permalink / raw)
To: acme, alexander.shishkin, bpf, jolsa, linux-kernel,
linux-perf-users, mark.rutland, mingo, namhyung, netdev, peterz,
syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: 13e3c7793e2f Merge tag 'for-netdev' of https://git.kernel...
git tree: bpf
console+strace: https://syzkaller.appspot.com/x/log.txt?x=177df7e0480000
kernel config: https://syzkaller.appspot.com/x/.config?x=b0e91ad4b5f69c47
dashboard link: https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15e87100480000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ceeb13880000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/373a99daa295/disk-13e3c779.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7fa71ed0fe17/vmlinux-13e3c779.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2842ad5c698b/bzImage-13e3c779.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b8e8c01c8ade4fe6e48f@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x3ee7/0x56d0 kernel/locking/lockdep.c:4925
Read of size 8 at addr ffff8880237d6018 by task syz-executor287/8300
CPU: 0 PID: 8300 Comm: syz-executor287 Not tainted 6.1.0-syzkaller-09661-g13e3c7793e2f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:284 [inline]
print_report+0x15e/0x45d mm/kasan/report.c:395
kasan_report+0xbf/0x1f0 mm/kasan/report.c:495
__lock_acquire+0x3ee7/0x56d0 kernel/locking/lockdep.c:4925
lock_acquire kernel/locking/lockdep.c:5668 [inline]
lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:162
put_pmu_ctx kernel/events/core.c:4913 [inline]
put_pmu_ctx+0xad/0x390 kernel/events/core.c:4893
_free_event+0x3c5/0x13d0 kernel/events/core.c:5196
free_event+0x58/0xc0 kernel/events/core.c:5224
__do_sys_perf_event_open+0x66d/0x2980 kernel/events/core.c:12701
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f3a2b1b3f29
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff4215df68 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00000000000f4240 RCX: 00007f3a2b1b3f29
RDX: 0000000000000000 RSI: 0000000000002070 RDI: 0000000020000480
RBP: 0000000000000000 R08: 0000000000000008 R09: 0000000000000001
R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000012a59
R13: 00007fff4215df7c R14: 00007fff4215df90 R15: 00007fff4215df80
</TASK>
Allocated by task 8300:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:371 [inline]
____kasan_kmalloc mm/kasan/common.c:330 [inline]
__kasan_kmalloc+0xa5/0xb0 mm/kasan/common.c:380
kmalloc include/linux/slab.h:580 [inline]
kzalloc include/linux/slab.h:720 [inline]
alloc_perf_context kernel/events/core.c:4693 [inline]
find_get_context+0xcc/0x810 kernel/events/core.c:4763
__do_sys_perf_event_open+0x963/0x2980 kernel/events/core.c:12476
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
Freed by task 5310:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
kasan_save_free_info+0x2e/0x40 mm/kasan/generic.c:518
____kasan_slab_free mm/kasan/common.c:236 [inline]
____kasan_slab_free+0x160/0x1c0 mm/kasan/common.c:200
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1781 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1807
slab_free mm/slub.c:3787 [inline]
__kmem_cache_free+0xaf/0x3b0 mm/slub.c:3800
rcu_do_batch kernel/rcu/tree.c:2244 [inline]
rcu_core+0x81f/0x1980 kernel/rcu/tree.c:2504
__do_softirq+0x1fb/0xadc kernel/softirq.c:571
Last potentially related work creation:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
__kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:488
__call_rcu_common.constprop.0+0x99/0x820 kernel/rcu/tree.c:2753
put_ctx kernel/events/core.c:1180 [inline]
put_ctx+0x116/0x1e0 kernel/events/core.c:1173
perf_event_exit_task_context kernel/events/core.c:13046 [inline]
perf_event_exit_task+0x556/0x760 kernel/events/core.c:13073
do_exit+0xb4d/0x2a30 kernel/exit.c:829
__do_sys_exit kernel/exit.c:917 [inline]
__se_sys_exit kernel/exit.c:915 [inline]
__x64_sys_exit+0x42/0x50 kernel/exit.c:915
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
The buggy address belongs to the object at ffff8880237d6000
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 24 bytes inside of
512-byte region [ffff8880237d6000, ffff8880237d6200)
The buggy address belongs to the physical page:
page:ffffea00008df500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x237d4
head:ffffea00008df500 order:2 compound_mapcount:0 compound_pincount:0
anon flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffff888012441c80 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 2173, tgid 2173 (kworker/u4:3), ts 10211275854, free_ts 0
prep_new_page mm/page_alloc.c:2539 [inline]
get_page_from_freelist+0x10b5/0x2d50 mm/page_alloc.c:4291
__alloc_pages+0x1cb/0x5b0 mm/page_alloc.c:5558
alloc_pages+0x1aa/0x270 mm/mempolicy.c:2285
alloc_slab_page mm/slub.c:1851 [inline]
allocate_slab+0x25f/0x350 mm/slub.c:1998
new_slab mm/slub.c:2051 [inline]
___slab_alloc+0xa91/0x1400 mm/slub.c:3193
__slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3292
__slab_alloc_node mm/slub.c:3345 [inline]
slab_alloc_node mm/slub.c:3442 [inline]
__kmem_cache_alloc_node+0x1a4/0x430 mm/slub.c:3491
kmalloc_trace+0x26/0x60 mm/slab_common.c:1062
kmalloc include/linux/slab.h:580 [inline]
kzalloc include/linux/slab.h:720 [inline]
alloc_bprm+0x51/0x900 fs/exec.c:1510
kernel_execve+0xaf/0x500 fs/exec.c:1981
call_usermodehelper_exec_async+0x2e7/0x580 kernel/umh.c:113
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
page_owner free stack trace missing
Memory state around the buggy address:
ffff8880237d5f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880237d5f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880237d6000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880237d6080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880237d6100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches
^ permalink raw reply [flat|nested] 15+ messages in thread* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-19 8:04 [syzbot] KASAN: use-after-free Read in put_pmu_ctx syzbot @ 2022-12-19 14:40 ` Peter Zijlstra 2022-12-19 19:33 ` sdf 2022-12-21 2:42 ` Chengming Zhou 2022-12-20 8:25 ` Peter Zijlstra 1 sibling, 2 replies; 15+ messages in thread From: Peter Zijlstra @ 2022-12-19 14:40 UTC (permalink / raw) To: syzbot Cc: acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, syzkaller-bugs On Mon, Dec 19, 2022 at 12:04:43AM -0800, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 13e3c7793e2f Merge tag 'for-netdev' of https://git.kernel... > git tree: bpf > console+strace: https://syzkaller.appspot.com/x/log.txt?x=177df7e0480000 > kernel config: https://syzkaller.appspot.com/x/.config?x=b0e91ad4b5f69c47 > dashboard link: https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15e87100480000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ceeb13880000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/373a99daa295/disk-13e3c779.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/7fa71ed0fe17/vmlinux-13e3c779.xz > kernel image: https://storage.googleapis.com/syzbot-assets/2842ad5c698b/bzImage-13e3c779.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+b8e8c01c8ade4fe6e48f@syzkaller.appspotmail.com > > ================================================================== > BUG: KASAN: use-after-free in __lock_acquire+0x3ee7/0x56d0 kernel/locking/lockdep.c:4925 > Read of size 8 at addr ffff8880237d6018 by task syz-executor287/8300 > > CPU: 0 PID: 8300 Comm: syz-executor287 Not tainted 6.1.0-syzkaller-09661-g13e3c7793e2f #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106 > print_address_description mm/kasan/report.c:284 [inline] > print_report+0x15e/0x45d mm/kasan/report.c:395 > kasan_report+0xbf/0x1f0 mm/kasan/report.c:495 > __lock_acquire+0x3ee7/0x56d0 kernel/locking/lockdep.c:4925 > lock_acquire kernel/locking/lockdep.c:5668 [inline] > lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633 > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] > _raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:162 > put_pmu_ctx kernel/events/core.c:4913 [inline] > put_pmu_ctx+0xad/0x390 kernel/events/core.c:4893 > _free_event+0x3c5/0x13d0 kernel/events/core.c:5196 > free_event+0x58/0xc0 kernel/events/core.c:5224 > __do_sys_perf_event_open+0x66d/0x2980 kernel/events/core.c:12701 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd Does this help? diff --git a/kernel/events/core.c b/kernel/events/core.c index e47914ac8732..bbff551783e1 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -12689,7 +12689,8 @@ SYSCALL_DEFINE5(perf_event_open, return event_fd; err_context: - /* event->pmu_ctx freed by free_event() */ + put_pmu_ctx(event->pmu_ctx); + event->pmu_ctx = NULL; /* _free_event() */ err_locked: mutex_unlock(&ctx->mutex); perf_unpin_context(ctx); ^ permalink raw reply related [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-19 14:40 ` Peter Zijlstra @ 2022-12-19 19:33 ` sdf 2022-12-19 19:56 ` syzbot 2022-12-20 8:22 ` Peter Zijlstra 2022-12-21 2:42 ` Chengming Zhou 1 sibling, 2 replies; 15+ messages in thread From: sdf @ 2022-12-19 19:33 UTC (permalink / raw) To: Peter Zijlstra Cc: syzbot, acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, syzkaller-bugs On 12/19, Peter Zijlstra wrote: > On Mon, Dec 19, 2022 at 12:04:43AM -0800, syzbot wrote: > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 13e3c7793e2f Merge tag 'for-netdev' of > https://git.kernel... > > git tree: bpf > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=177df7e0480000 > > kernel config: > https://syzkaller.appspot.com/x/.config?x=b0e91ad4b5f69c47 > > dashboard link: > https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU > Binutils for Debian) 2.35.2 > > syz repro: > https://syzkaller.appspot.com/x/repro.syz?x=15e87100480000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ceeb13880000 > > > > Downloadable assets: > > disk image: > https://storage.googleapis.com/syzbot-assets/373a99daa295/disk-13e3c779.raw.xz > > vmlinux: > https://storage.googleapis.com/syzbot-assets/7fa71ed0fe17/vmlinux-13e3c779.xz > > kernel image: > https://storage.googleapis.com/syzbot-assets/2842ad5c698b/bzImage-13e3c779.xz > > > > IMPORTANT: if you fix the issue, please add the following tag to the > commit: > > Reported-by: syzbot+b8e8c01c8ade4fe6e48f@syzkaller.appspotmail.com > > > > ================================================================== > > BUG: KASAN: use-after-free in __lock_acquire+0x3ee7/0x56d0 > kernel/locking/lockdep.c:4925 > > Read of size 8 at addr ffff8880237d6018 by task syz-executor287/8300 > > > > CPU: 0 PID: 8300 Comm: syz-executor287 Not tainted > 6.1.0-syzkaller-09661-g13e3c7793e2f #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 10/26/2022 > > Call Trace: > > <TASK> > > __dump_stack lib/dump_stack.c:88 [inline] > > dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106 > > print_address_description mm/kasan/report.c:284 [inline] > > print_report+0x15e/0x45d mm/kasan/report.c:395 > > kasan_report+0xbf/0x1f0 mm/kasan/report.c:495 > > __lock_acquire+0x3ee7/0x56d0 kernel/locking/lockdep.c:4925 > > lock_acquire kernel/locking/lockdep.c:5668 [inline] > > lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633 > > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] > > _raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:162 > > put_pmu_ctx kernel/events/core.c:4913 [inline] > > put_pmu_ctx+0xad/0x390 kernel/events/core.c:4893 > > _free_event+0x3c5/0x13d0 kernel/events/core.c:5196 > > free_event+0x58/0xc0 kernel/events/core.c:5224 > > __do_sys_perf_event_open+0x66d/0x2980 kernel/events/core.c:12701 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > Does this help? Let's maybe try it this way: #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git 13e3c7793e2f diff --git a/kernel/events/core.c b/kernel/events/core.c index e47914ac8732..bbff551783e1 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -12689,7 +12689,8 @@ SYSCALL_DEFINE5(perf_event_open, return event_fd; err_context: - /* event->pmu_ctx freed by free_event() */ + put_pmu_ctx(event->pmu_ctx); + event->pmu_ctx = NULL; /* _free_event() */ err_locked: mutex_unlock(&ctx->mutex); perf_unpin_context(ctx); ^ permalink raw reply related [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-19 19:33 ` sdf @ 2022-12-19 19:56 ` syzbot 2022-12-19 21:33 ` sdf 2022-12-20 8:22 ` Peter Zijlstra 1 sibling, 1 reply; 15+ messages in thread From: syzbot @ 2022-12-19 19:56 UTC (permalink / raw) To: acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, peterz, sdf, syzkaller-bugs Hello, syzbot tried to test the proposed patch but the build/boot failed: failed to apply patch: checking file kernel/events/core.c patch: **** unexpected end of file in patch Tested on: commit: 13e3c779 Merge tag 'for-netdev' of https://git.kernel... git tree: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git dashboard link: https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f compiler: patch: https://syzkaller.appspot.com/x/patch.diff?x=15861a9f880000 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-19 19:56 ` syzbot @ 2022-12-19 21:33 ` sdf 2022-12-19 22:24 ` syzbot 0 siblings, 1 reply; 15+ messages in thread From: sdf @ 2022-12-19 21:33 UTC (permalink / raw) To: syzbot Cc: acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, peterz, syzkaller-bugs On 12/19, syzbot wrote: > Hello, > syzbot tried to test the proposed patch but the build/boot failed: > failed to apply patch: > checking file kernel/events/core.c > patch: **** unexpected end of file in patch > Tested on: > commit: 13e3c779 Merge tag 'for-netdev' of https://git.kernel... > git tree: > https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git > dashboard link: > https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f > compiler: > patch: > https://syzkaller.appspot.com/x/patch.diff?x=15861a9f880000 Let's try again with hopefully a better formatted patch.. #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git 13e3c7793e2f diff --git a/kernel/events/core.c b/kernel/events/core.c index e47914ac8732..bbff551783e1 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -12689,7 +12689,8 @@ SYSCALL_DEFINE5(perf_event_open, return event_fd; err_context: - /* event->pmu_ctx freed by free_event() */ + put_pmu_ctx(event->pmu_ctx); + event->pmu_ctx = NULL; /* _free_event() */ err_locked: mutex_unlock(&ctx->mutex); perf_unpin_context(ctx); ^ permalink raw reply related [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-19 21:33 ` sdf @ 2022-12-19 22:24 ` syzbot 0 siblings, 0 replies; 15+ messages in thread From: syzbot @ 2022-12-19 22:24 UTC (permalink / raw) To: acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, peterz, sdf, syzkaller-bugs Hello, syzbot tried to test the proposed patch but the build/boot failed: failed to apply patch: checking file kernel/events/core.c patch: **** unexpected end of file in patch Tested on: commit: 13e3c779 Merge tag 'for-netdev' of https://git.kernel... git tree: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git dashboard link: https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f compiler: patch: https://syzkaller.appspot.com/x/patch.diff?x=1451cef0480000 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-19 19:33 ` sdf 2022-12-19 19:56 ` syzbot @ 2022-12-20 8:22 ` Peter Zijlstra 2022-12-20 17:10 ` Stanislav Fomichev 1 sibling, 1 reply; 15+ messages in thread From: Peter Zijlstra @ 2022-12-20 8:22 UTC (permalink / raw) To: sdf Cc: syzbot, acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, syzkaller-bugs On Mon, Dec 19, 2022 at 11:33:29AM -0800, sdf@google.com wrote: > On 12/19, Peter Zijlstra wrote: > > On Mon, Dec 19, 2022 at 12:04:43AM -0800, syzbot wrote: > > > HEAD commit: 13e3c7793e2f Merge tag 'for-netdev' of > > https://git.kernel... > > > git tree: bpf > > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=177df7e0480000 > > > kernel config: > > https://syzkaller.appspot.com/x/.config?x=b0e91ad4b5f69c47 > > > dashboard link: > > https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f ^ so syzbot knows what tree and config were used to trigger the report, then why: > Let's maybe try it this way: > > #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git > 13e3c7793e2f do you have to repeat that again in order for it to test something? ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-20 8:22 ` Peter Zijlstra @ 2022-12-20 17:10 ` Stanislav Fomichev 2022-12-20 19:37 ` syzbot 0 siblings, 1 reply; 15+ messages in thread From: Stanislav Fomichev @ 2022-12-20 17:10 UTC (permalink / raw) To: Peter Zijlstra Cc: syzbot, acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, syzkaller-bugs [-- Attachment #1: Type: text/plain, Size: 1343 bytes --] On Tue, Dec 20, 2022 at 12:22 AM Peter Zijlstra <peterz@infradead.org> wrote: > > On Mon, Dec 19, 2022 at 11:33:29AM -0800, sdf@google.com wrote: > > On 12/19, Peter Zijlstra wrote: > > > On Mon, Dec 19, 2022 at 12:04:43AM -0800, syzbot wrote: > > > > > HEAD commit: 13e3c7793e2f Merge tag 'for-netdev' of > > > https://git.kernel... > > > > git tree: bpf > > > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=177df7e0480000 > > > > kernel config: > > > https://syzkaller.appspot.com/x/.config?x=b0e91ad4b5f69c47 > > > > dashboard link: > > > https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f > > ^ so syzbot knows what tree and config were used to trigger the report, > then why: I haven't used it before and wasn't sure whether it would take the last commit from the branch of the one where it failed. Adding them shouldn't hurt, right? > > Let's maybe try it this way: > > > > #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git > > 13e3c7793e2f > > do you have to repeat that again in order for it to test something? Yeah, I was trying to understand why it doesn't like my patch. It seems I can retry with the patch attached which hopefully should fix the possible formatting issue; let's see. #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git 13e3c7793e2f [-- Attachment #2: pmu.patch --] [-- Type: text/x-patch, Size: 433 bytes --] diff --git a/kernel/events/core.c b/kernel/events/core.c index e47914ac8732..bbff551783e1 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -12689,7 +12689,8 @@ SYSCALL_DEFINE5(perf_event_open, return event_fd; err_context: - /* event->pmu_ctx freed by free_event() */ + put_pmu_ctx(event->pmu_ctx); + event->pmu_ctx = NULL; /* _free_event() */ err_locked: mutex_unlock(&ctx->mutex); perf_unpin_context(ctx); ^ permalink raw reply related [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-20 17:10 ` Stanislav Fomichev @ 2022-12-20 19:37 ` syzbot 0 siblings, 0 replies; 15+ messages in thread From: syzbot @ 2022-12-20 19:37 UTC (permalink / raw) To: acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, peterz, sdf, syzkaller-bugs Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: INFO: rcu detected stall in corrupted rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { P5778 } 2673 jiffies s: 2773 root: 0x0/T rcu: blocking rcu_node structures (internal RCU debug): Tested on: commit: 13e3c779 Merge tag 'for-netdev' of https://git.kernel... git tree: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git console output: https://syzkaller.appspot.com/x/log.txt?x=12cb0e5d880000 kernel config: https://syzkaller.appspot.com/x/.config?x=b0e91ad4b5f69c47 dashboard link: https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 patch: https://syzkaller.appspot.com/x/patch.diff?x=12df6a9b880000 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-19 14:40 ` Peter Zijlstra 2022-12-19 19:33 ` sdf @ 2022-12-21 2:42 ` Chengming Zhou 2022-12-22 20:59 ` Peter Zijlstra 1 sibling, 1 reply; 15+ messages in thread From: Chengming Zhou @ 2022-12-21 2:42 UTC (permalink / raw) To: Peter Zijlstra, syzbot Cc: acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, syzkaller-bugs On 2022/12/19 22:40, Peter Zijlstra wrote: > On Mon, Dec 19, 2022 at 12:04:43AM -0800, syzbot wrote: >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: 13e3c7793e2f Merge tag 'for-netdev' of https://git.kernel... >> git tree: bpf >> console+strace: https://syzkaller.appspot.com/x/log.txt?x=177df7e0480000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=b0e91ad4b5f69c47 >> dashboard link: https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f >> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15e87100480000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ceeb13880000 >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/373a99daa295/disk-13e3c779.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/7fa71ed0fe17/vmlinux-13e3c779.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/2842ad5c698b/bzImage-13e3c779.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+b8e8c01c8ade4fe6e48f@syzkaller.appspotmail.com >> >> ================================================================== >> BUG: KASAN: use-after-free in __lock_acquire+0x3ee7/0x56d0 kernel/locking/lockdep.c:4925 >> Read of size 8 at addr ffff8880237d6018 by task syz-executor287/8300 >> >> CPU: 0 PID: 8300 Comm: syz-executor287 Not tainted 6.1.0-syzkaller-09661-g13e3c7793e2f #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 >> Call Trace: >> <TASK> >> __dump_stack lib/dump_stack.c:88 [inline] >> dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106 >> print_address_description mm/kasan/report.c:284 [inline] >> print_report+0x15e/0x45d mm/kasan/report.c:395 >> kasan_report+0xbf/0x1f0 mm/kasan/report.c:495 >> __lock_acquire+0x3ee7/0x56d0 kernel/locking/lockdep.c:4925 >> lock_acquire kernel/locking/lockdep.c:5668 [inline] >> lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633 >> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] >> _raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:162 >> put_pmu_ctx kernel/events/core.c:4913 [inline] >> put_pmu_ctx+0xad/0x390 kernel/events/core.c:4893 >> _free_event+0x3c5/0x13d0 kernel/events/core.c:5196 >> free_event+0x58/0xc0 kernel/events/core.c:5224 >> __do_sys_perf_event_open+0x66d/0x2980 kernel/events/core.c:12701 >> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 >> entry_SYSCALL_64_after_hwframe+0x63/0xcd > > Does this help? > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index e47914ac8732..bbff551783e1 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -12689,7 +12689,8 @@ SYSCALL_DEFINE5(perf_event_open, > return event_fd; > > err_context: > - /* event->pmu_ctx freed by free_event() */ > + put_pmu_ctx(event->pmu_ctx); > + event->pmu_ctx = NULL; /* _free_event() */ > err_locked: > mutex_unlock(&ctx->mutex); > perf_unpin_context(ctx); Tested-by: Chengming Zhou <zhouchengming@bytedance.com> While reviewing the code, I found perf_event_create_kernel_counter() has the similar problem in the "err_pmu_ctx" error handling path: CPU0 CPU1 perf_event_create_kernel_counter() // inc ctx refcnt find_get_context(task, event) (1) // inc pmu_ctx refcnt pmu_ctx = find_get_pmu_context() event->pmu_ctx = pmu_ctx ... goto err_pmu_ctx: // dec pmu_ctx refcnt put_pmu_ctx(pmu_ctx) (2) mutex_unlock(&ctx->mutex) // dec ctx refcnt put_ctx(ctx) perf_event_exit_task_context() mutex_lock() mutex_unlock() // last refcnt put put_ctx() free_event(event) if (event->pmu_ctx) // True put_pmu_ctx() (3) // will access freed pmu_ctx or ctx if (event->ctx) // False put_ctx() (3) has UAF problem since the pmu_ctx maybe freed in (2), so also should have "event->pmu_ctx = NULL;" in (2). ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-21 2:42 ` Chengming Zhou @ 2022-12-22 20:59 ` Peter Zijlstra 2022-12-23 10:08 ` Chengming Zhou 0 siblings, 1 reply; 15+ messages in thread From: Peter Zijlstra @ 2022-12-22 20:59 UTC (permalink / raw) To: Chengming Zhou Cc: syzbot, acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, syzkaller-bugs On Wed, Dec 21, 2022 at 10:42:39AM +0800, Chengming Zhou wrote: > > Does this help? > > > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > index e47914ac8732..bbff551783e1 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -12689,7 +12689,8 @@ SYSCALL_DEFINE5(perf_event_open, > > return event_fd; > > > > err_context: > > - /* event->pmu_ctx freed by free_event() */ > > + put_pmu_ctx(event->pmu_ctx); > > + event->pmu_ctx = NULL; /* _free_event() */ > > err_locked: > > mutex_unlock(&ctx->mutex); > > perf_unpin_context(ctx); > > Tested-by: Chengming Zhou <zhouchengming@bytedance.com> > > While reviewing the code, I found perf_event_create_kernel_counter() > has the similar problem in the "err_pmu_ctx" error handling path: Right you are, updated the patch, thanks! > CPU0 CPU1 > perf_event_create_kernel_counter() > // inc ctx refcnt > find_get_context(task, event) (1) > > // inc pmu_ctx refcnt > pmu_ctx = find_get_pmu_context() > > event->pmu_ctx = pmu_ctx > ... > goto err_pmu_ctx: > // dec pmu_ctx refcnt > put_pmu_ctx(pmu_ctx) (2) > > mutex_unlock(&ctx->mutex) > // dec ctx refcnt > put_ctx(ctx) > perf_event_exit_task_context() > mutex_lock() > mutex_unlock() > // last refcnt put > put_ctx() > free_event(event) > if (event->pmu_ctx) // True > put_pmu_ctx() (3) > // will access freed pmu_ctx or ctx > > if (event->ctx) // False > put_ctx() This doesn't look right; iirc you can hit this without concurrency, something like so: // note that when getting here, we've not passed // perf_install_in_context() and event->ctx == NULL. err_pmu_ctx: put_pmu_ctx(); put_ctx(); // last, actually frees ctx .. err_alloc: free_event() _free_event() if (event->pmu_ctx) // true, because we forgot to clear put_pmu_ctx() // hits 0 because double put // goes and touch epc->ctx and UaF ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-22 20:59 ` Peter Zijlstra @ 2022-12-23 10:08 ` Chengming Zhou 0 siblings, 0 replies; 15+ messages in thread From: Chengming Zhou @ 2022-12-23 10:08 UTC (permalink / raw) To: Peter Zijlstra Cc: syzbot, acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, syzkaller-bugs On 2022/12/23 04:59, Peter Zijlstra wrote: > On Wed, Dec 21, 2022 at 10:42:39AM +0800, Chengming Zhou wrote: > >>> Does this help? >>> >>> diff --git a/kernel/events/core.c b/kernel/events/core.c >>> index e47914ac8732..bbff551783e1 100644 >>> --- a/kernel/events/core.c >>> +++ b/kernel/events/core.c >>> @@ -12689,7 +12689,8 @@ SYSCALL_DEFINE5(perf_event_open, >>> return event_fd; >>> >>> err_context: >>> - /* event->pmu_ctx freed by free_event() */ >>> + put_pmu_ctx(event->pmu_ctx); >>> + event->pmu_ctx = NULL; /* _free_event() */ >>> err_locked: >>> mutex_unlock(&ctx->mutex); >>> perf_unpin_context(ctx); >> >> Tested-by: Chengming Zhou <zhouchengming@bytedance.com> >> >> While reviewing the code, I found perf_event_create_kernel_counter() >> has the similar problem in the "err_pmu_ctx" error handling path: > > Right you are, updated the patch, thanks! > >> CPU0 CPU1 >> perf_event_create_kernel_counter() >> // inc ctx refcnt >> find_get_context(task, event) (1) >> >> // inc pmu_ctx refcnt >> pmu_ctx = find_get_pmu_context() >> >> event->pmu_ctx = pmu_ctx >> ... >> goto err_pmu_ctx: >> // dec pmu_ctx refcnt >> put_pmu_ctx(pmu_ctx) (2) >> >> mutex_unlock(&ctx->mutex) >> // dec ctx refcnt >> put_ctx(ctx) >> perf_event_exit_task_context() >> mutex_lock() >> mutex_unlock() >> // last refcnt put >> put_ctx() >> free_event(event) >> if (event->pmu_ctx) // True >> put_pmu_ctx() (3) >> // will access freed pmu_ctx or ctx >> >> if (event->ctx) // False >> put_ctx() > > This doesn't look right; iirc you can hit this without concurrency, > something like so: Right, pmu_ctx UaF can hit without concurrency. But ctx has been created with refcnt == 1, which referenced by the task, so the last refcnt put must be in perf_event_exit_task_context(). Maybe we can improve this, don't let ctx referenced by the task? Then ctx can be freed when all perf_events are removed, instead of having to wait for the task to exit. Maybe I missed something... > > > // note that when getting here, we've not passed > // perf_install_in_context() and event->ctx == NULL. > err_pmu_ctx: > put_pmu_ctx(); > put_ctx(); // last, actually frees ctx This put_ctx() dec refcnt from 2 to 1, perf_event_exit_task_context() will put the last refcnt and free it. > .. > err_alloc: > free_event() > _free_event() > if (event->pmu_ctx) // true, because we forgot to clear > put_pmu_ctx() // hits 0 because double put > // goes and touch epc->ctx and UaF > > ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-19 8:04 [syzbot] KASAN: use-after-free Read in put_pmu_ctx syzbot 2022-12-19 14:40 ` Peter Zijlstra @ 2022-12-20 8:25 ` Peter Zijlstra 2022-12-20 8:43 ` syzbot 1 sibling, 1 reply; 15+ messages in thread From: Peter Zijlstra @ 2022-12-20 8:25 UTC (permalink / raw) To: syzbot Cc: acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, syzkaller-bugs On Mon, Dec 19, 2022 at 12:04:43AM -0800, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 13e3c7793e2f Merge tag 'for-netdev' of https://git.kernel... > git tree: bpf > console+strace: https://syzkaller.appspot.com/x/log.txt?x=177df7e0480000 > kernel config: https://syzkaller.appspot.com/x/.config?x=b0e91ad4b5f69c47 > dashboard link: https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15e87100480000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ceeb13880000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/373a99daa295/disk-13e3c779.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/7fa71ed0fe17/vmlinux-13e3c779.xz > kernel image: https://storage.googleapis.com/syzbot-assets/2842ad5c698b/bzImage-13e3c779.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+b8e8c01c8ade4fe6e48f@syzkaller.appspotmail.com > > ================================================================== > BUG: KASAN: use-after-free in __lock_acquire+0x3ee7/0x56d0 kernel/locking/lockdep.c:4925 > Read of size 8 at addr ffff8880237d6018 by task syz-executor287/8300 OK, lemme try this.. still think having to repeat the tree it already has is daft.. #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git 13e3c7793e2f diff --git a/kernel/events/core.c b/kernel/events/core.c index eacc3702654d..7da593504c5b 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -12689,7 +12689,8 @@ SYSCALL_DEFINE5(perf_event_open, return event_fd; err_context: - /* event->pmu_ctx freed by free_event() */ + put_pmu_ctx(event->pmu_ctx); + event->pmu_ctx = NULL; /* _free_event() */ err_locked: mutex_unlock(&ctx->mutex); perf_unpin_context(ctx); ^ permalink raw reply related [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-20 8:25 ` Peter Zijlstra @ 2022-12-20 8:43 ` syzbot 2022-12-20 10:04 ` Peter Zijlstra 0 siblings, 1 reply; 15+ messages in thread From: syzbot @ 2022-12-20 8:43 UTC (permalink / raw) To: acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, peterz, syzkaller-bugs Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: INFO: rcu detected stall in corrupted rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { P5791 } 2673 jiffies s: 2805 root: 0x0/T rcu: blocking rcu_node structures (internal RCU debug): Tested on: commit: 13e3c779 Merge tag 'for-netdev' of https://git.kernel... git tree: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git console output: https://syzkaller.appspot.com/x/log.txt?x=121ea2e8480000 kernel config: https://syzkaller.appspot.com/x/.config?x=b0e91ad4b5f69c47 dashboard link: https://syzkaller.appspot.com/bug?extid=b8e8c01c8ade4fe6e48f compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 patch: https://syzkaller.appspot.com/x/patch.diff?x=12d4ad4f880000 ^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [syzbot] KASAN: use-after-free Read in put_pmu_ctx 2022-12-20 8:43 ` syzbot @ 2022-12-20 10:04 ` Peter Zijlstra 0 siblings, 0 replies; 15+ messages in thread From: Peter Zijlstra @ 2022-12-20 10:04 UTC (permalink / raw) To: syzbot Cc: acme, alexander.shishkin, bpf, jolsa, linux-kernel, linux-perf-users, mark.rutland, mingo, namhyung, netdev, syzkaller-bugs On Tue, Dec 20, 2022 at 12:43:25AM -0800, syzbot wrote: > Hello, > > syzbot has tested the proposed patch but the reproducer is still triggering an issue: > INFO: rcu detected stall in corrupted > > rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { P5791 } 2673 jiffies s: 2805 root: 0x0/T > rcu: blocking rcu_node structures (internal RCU debug): That is an entirely different issue methinks. Let me go write up a Changelog for that thing and stuff it somewhere /urgent. ^ permalink raw reply [flat|nested] 15+ messages in thread
end of thread, other threads:[~2022-12-23 10:08 UTC | newest] Thread overview: 15+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2022-12-19 8:04 [syzbot] KASAN: use-after-free Read in put_pmu_ctx syzbot 2022-12-19 14:40 ` Peter Zijlstra 2022-12-19 19:33 ` sdf 2022-12-19 19:56 ` syzbot 2022-12-19 21:33 ` sdf 2022-12-19 22:24 ` syzbot 2022-12-20 8:22 ` Peter Zijlstra 2022-12-20 17:10 ` Stanislav Fomichev 2022-12-20 19:37 ` syzbot 2022-12-21 2:42 ` Chengming Zhou 2022-12-22 20:59 ` Peter Zijlstra 2022-12-23 10:08 ` Chengming Zhou 2022-12-20 8:25 ` Peter Zijlstra 2022-12-20 8:43 ` syzbot 2022-12-20 10:04 ` Peter Zijlstra
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).