Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751145AbeAOXBN (ORCPT + 1 other); Mon, 15 Jan 2018 18:01:13 -0500 Received: from www62.your-server.de ([213.133.104.62]:50231 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750764AbeAOXBM (ORCPT ); Mon, 15 Jan 2018 18:01:12 -0500 Subject: Re: KASAN: use-after-free Write in array_map_update_elem To: Dmitry Vyukov , syzbot Cc: Alexei Starovoitov , LKML , netdev , syzkaller-bugs@googlegroups.com References: <001a1144b7fe3898b00562d1d71f@google.com> From: Daniel Borkmann Message-ID: <9f4a404d-ad9f-e2cd-d0a5-dd37be807e3c@iogearbox.net> Date: Tue, 16 Jan 2018 00:01:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On 01/15/2018 04:07 PM, Dmitry Vyukov wrote: > On Mon, Jan 15, 2018 at 3:58 PM, syzbot > wrote: >> Hello, >> >> syzkaller hit the following crash on >> 8418f88764046d0e8ca6a3c04a69a0e57189aa1e >> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master >> compiler: gcc (GCC) 7.1.1 20170620 >> .config is attached >> Raw console output is attached. >> C reproducer is attached >> syzkaller reproducer is attached. See https://goo.gl/kgGztJ >> for information about syzkaller reproducers >> >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+a2215ab5e92b3bb1c95f@syzkaller.appspotmail.com >> It will help syzbot understand when the bug is fixed. See footer for >> details. >> If you forward the report, please keep this part and the footer. >> >> audit: type=1400 audit(1515680378.393:8): avc: denied { sys_admin } for >> pid=3508 comm="syzkaller203412" capability=21 >> scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 >> tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns >> permissive=1 >> audit: type=1400 audit(1515680378.446:9): avc: denied { sys_chroot } for >> pid=3509 comm="syzkaller203412" capability=18 >> scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 >> tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns >> permissive=1 >> ================================================================== >> BUG: KASAN: use-after-free in memcpy include/linux/string.h:344 [inline] >> BUG: KASAN: use-after-free in array_map_update_elem+0x197/0x240 >> kernel/bpf/arraymap.c:249 >> Write of size 1 at addr ffff8801cb125bc0 by task syzkaller203412/3509 >> >> CPU: 1 PID: 3509 Comm: syzkaller203412 Not tainted 4.15.0-rc7-next-20180111+ >> #94 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS >> Google 01/01/2011 >> Call Trace: >> __dump_stack lib/dump_stack.c:17 [inline] >> dump_stack+0x194/0x257 lib/dump_stack.c:53 >> print_address_description+0x73/0x250 mm/kasan/report.c:256 >> kasan_report_error mm/kasan/report.c:354 [inline] >> kasan_report+0x23b/0x360 mm/kasan/report.c:412 >> check_memory_region_inline mm/kasan/kasan.c:260 [inline] >> check_memory_region+0x137/0x190 mm/kasan/kasan.c:267 >> memcpy+0x37/0x50 mm/kasan/kasan.c:303 >> memcpy include/linux/string.h:344 [inline] >> array_map_update_elem+0x197/0x240 kernel/bpf/arraymap.c:249 >> map_update_elem kernel/bpf/syscall.c:687 [inline] >> SYSC_bpf kernel/bpf/syscall.c:1811 [inline] >> SyS_bpf+0x32df/0x4400 kernel/bpf/syscall.c:1782 >> entry_SYSCALL_64_fastpath+0x29/0xa0 >> RIP: 0033:0x440ac9 >> RSP: 002b:00000000007dff68 EFLAGS: 00000203 ORIG_RAX: 0000000000000141 >> RAX: ffffffffffffffda RBX: 00007ffe6a583b10 RCX: 0000000000440ac9 >> RDX: 0000000000000020 RSI: 0000000020eaf000 RDI: 0000000000000002 >> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000203 R12: 00000000004022a0 >> R13: 0000000000402330 R14: 0000000000000000 R15: 0000000000000000 >> >> Allocated by task 3071: >> save_stack+0x43/0xd0 mm/kasan/kasan.c:447 >> set_track mm/kasan/kasan.c:459 [inline] >> kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552 >> kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489 >> kmem_cache_alloc+0x12e/0x760 mm/slab.c:3541 >> getname_flags+0xcb/0x580 fs/namei.c:138 >> user_path_at_empty+0x2d/0x50 fs/namei.c:2587 >> user_path_at include/linux/namei.h:57 [inline] >> SYSC_faccessat fs/open.c:384 [inline] >> SyS_faccessat fs/open.c:353 [inline] >> SYSC_access fs/open.c:431 [inline] >> SyS_access+0x22c/0x6a0 fs/open.c:429 >> entry_SYSCALL_64_fastpath+0x29/0xa0 >> >> Freed by task 3071: >> save_stack+0x43/0xd0 mm/kasan/kasan.c:447 >> set_track mm/kasan/kasan.c:459 [inline] >> __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520 >> kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527 >> __cache_free mm/slab.c:3485 [inline] >> kmem_cache_free+0x86/0x2b0 mm/slab.c:3743 >> putname+0xee/0x130 fs/namei.c:258 >> filename_lookup+0x315/0x500 fs/namei.c:2342 >> user_path_at_empty+0x40/0x50 fs/namei.c:2587 >> user_path_at include/linux/namei.h:57 [inline] >> SYSC_faccessat fs/open.c:384 [inline] >> SyS_faccessat fs/open.c:353 [inline] >> SYSC_access fs/open.c:431 [inline] >> SyS_access+0x22c/0x6a0 fs/open.c:429 >> entry_SYSCALL_64_fastpath+0x29/0xa0 >> >> The buggy address belongs to the object at ffff8801cb124e40 >> which belongs to the cache names_cache of size 4096 >> The buggy address is located 3456 bytes inside of >> 4096-byte region [ffff8801cb124e40, ffff8801cb125e40) >> The buggy address belongs to the page: >> page:ffffea00072c4900 count:1 mapcount:0 mapping:ffff8801cb124e40 index:0x0 >> compound_mapcount: 0 >> flags: 0x2fffc0000008100(slab|head) >> raw: 02fffc0000008100 ffff8801cb124e40 0000000000000000 0000000100000001 >> raw: ffffea000729bc20 ffffea000729bca0 ffff8801dae30600 0000000000000000 >> page dumped because: kasan: bad access detected >> >> Memory state around the buggy address: >> ffff8801cb125a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ffff8801cb125b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>> >>> ffff8801cb125b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> >> ^ >> ffff8801cb125c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ffff8801cb125c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ================================================================== > > > This is: > > #syz fix: > bpf, array: fix overflow in max_entries and undefined behavior in index_mask > > right? Yes, also correct. I just checked out both and the above linux-next tree doesn't have that fix included as well.