Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755882AbeAOPII (ORCPT + 1 other); Mon, 15 Jan 2018 10:08:08 -0500 Received: from mail-pl0-f68.google.com ([209.85.160.68]:43568 "EHLO mail-pl0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755862AbeAOPIF (ORCPT ); Mon, 15 Jan 2018 10:08:05 -0500 X-Google-Smtp-Source: ACJfBouG92mQLMHfqEaLSCpRQBu0fHkjROUZi3ZblipkeheVY/WtnN8UAcgGwR1pZNTSRaHOaP4bKUqh3D4GZknSzSk= MIME-Version: 1.0 In-Reply-To: <001a1144b7fe3898b00562d1d71f@google.com> References: <001a1144b7fe3898b00562d1d71f@google.com> From: Dmitry Vyukov Date: Mon, 15 Jan 2018 16:07:44 +0100 Message-ID: Subject: Re: KASAN: use-after-free Write in array_map_update_elem To: syzbot Cc: Alexei Starovoitov , Daniel Borkmann , LKML , netdev , syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: 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? > --- > This bug is generated by a dumb bot. It may contain errors. > See https://goo.gl/tpsmEJ for details. > Direct all questions to syzkaller@googlegroups.com. > > syzbot will keep track of this bug report. > If you forgot to add the Reported-by tag, once the fix for this bug is > merged > into any tree, please reply to this email with: > #syz fix: exact-commit-title > If you want to test a patch for this bug, please reply with: > #syz test: git://repo/address.git branch > and provide the patch inline or as an attachment. > To mark this as a duplicate of another syzbot report, please reply with: > #syz dup: exact-subject-of-another-report > If it's a one-off invalid bug report, please reply with: > #syz invalid > Note: if the crash happens again, it will cause creation of a new bug > report. > Note: all commands must start from beginning of the line in the email body. > > -- > You received this message because you are subscribed to the Google Groups > "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to syzkaller-bugs+unsubscribe@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/syzkaller-bugs/001a1144b7fe3898b00562d1d71f%40google.com. > For more options, visit https://groups.google.com/d/optout.