Hi Dmitry, On 01/11/2018 11:22 AM, Dmitry Vyukov wrote: > On Thu, Jan 11, 2018 at 11:17 AM, syzbot > <syzbot+d85bfb332db8f0794...@syzkaller.appspotmail.com> wrote: >> Hello, >> >> syzkaller hit the following crash on >> 4147d50978df60f34d444c647dde9e5b34a4315e >> git://git.cmpxchg.org/linux-mmots.git/master >> compiler: gcc (GCC) 7.1.1 20170620 >> .config is attached >> Raw console output is attached. >> Unfortunately, I don't have any reproducer for this bug yet. >> >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+d85bfb332db8f0794...@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. >> >> netlink: 3 bytes leftover after parsing attributes in process >> `syz-executor5'. >> ================================================================== >> BUG: KASAN: use-after-free in __bpf_prog_put+0x5e8/0x640 >> kernel/bpf/syscall.c:944 >> netlink: 'syz-executor5': attribute type 5 has an invalid length. >> Read of size 8 at addr ffff8801d3619658 by task syz-executor0/12398 >> >> CPU: 1 PID: 12398 Comm: syz-executor0 Not tainted 4.15.0-rc7-mm1+ #53 >> 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 >> __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 >> __bpf_prog_put+0x5e8/0x640 kernel/bpf/syscall.c:944 >> bpf_prog_put+0x1a/0x20 kernel/bpf/syscall.c:961 >> prog_fd_array_put_ptr+0x15/0x20 kernel/bpf/arraymap.c:446 >> fd_array_map_delete_elem+0xc8/0x110 kernel/bpf/arraymap.c:420 >> map_delete_elem kernel/bpf/syscall.c:737 [inline] >> SYSC_bpf kernel/bpf/syscall.c:1814 [inline] >> SyS_bpf+0x22ea/0x4400 kernel/bpf/syscall.c:1782 >> entry_SYSCALL_64_fastpath+0x29/0xa0 >> RIP: 0033:0x452ac9 >> RSP: 002b:00007fb70df60c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000141 >> RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ac9 >> RDX: 0000000000000010 RSI: 0000000020f02ff0 RDI: 0000000000000003 >> RBP: 00000000000003aa R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f3890 >> R13: 00000000ffffffff R14: 00007fb70df616d4 R15: 0000000000000000 >> >> Allocated by task 11996: >> 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 >> kmem_cache_zalloc include/linux/slab.h:694 [inline] >> get_empty_filp+0xfb/0x4f0 fs/file_table.c:122 >> path_openat+0xed/0x3530 fs/namei.c:3514 >> do_filp_open+0x25b/0x3b0 fs/namei.c:3572 >> do_sys_open+0x502/0x6d0 fs/open.c:1059 >> SYSC_open fs/open.c:1077 [inline] >> SyS_open+0x2d/0x40 fs/open.c:1072 >> entry_SYSCALL_64_fastpath+0x29/0xa0 >> >> Freed by task 11994: >> 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 >> file_free_rcu+0x5c/0x70 fs/file_table.c:49 >> __rcu_reclaim kernel/rcu/rcu.h:172 [inline] >> rcu_do_batch kernel/rcu/tree.c:2675 [inline] >> invoke_rcu_callbacks kernel/rcu/tree.c:2934 [inline] >> __rcu_process_callbacks kernel/rcu/tree.c:2901 [inline] >> rcu_process_callbacks+0xd6c/0x17f0 kernel/rcu/tree.c:2918 >> __do_softirq+0x2d7/0xb85 kernel/softirq.c:285 >> >> The buggy address belongs to the object at ffff8801d36195c0 >> which belongs to the cache filp of size 456 >> The buggy address is located 152 bytes inside of >> 456-byte region [ffff8801d36195c0, ffff8801d3619788) >> The buggy address belongs to the page: >> page:ffffea00074d8640 count:1 mapcount:0 mapping:ffff8801d36190c0 index:0x0 >> flags: 0x2fffc0000000100(slab) >> raw: 02fffc0000000100 ffff8801d36190c0 0000000000000000 0000000100000006 >> raw: ffffea00074c49a0 ffffea000747a160 ffff8801dae30180 0000000000000000 >> page dumped because: kasan: bad access detected >> >> Memory state around the buggy address: >> ffff8801d3619500: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> ffff8801d3619580: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb >>> >>> ffff8801d3619600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> >> ^ >> ffff8801d3619680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ffff8801d3619700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ================================================================== > > > Is it the same as "general protection fault in __bpf_prog_put"? > https://groups.google.com/forum/#!topic/syzkaller-bugs/jUsNMmVgms0 > > The first stack looks similar, but alloc/free stacks looks unrelated. > What's the root cause of this? Is prog->aux an uninitialized pointer? > I wonder if initializing memory in kmalloc would help to prevent this > bug from duplicating? E.g. if we init memory to 0, it would always > cause GPFs, or if we init to an invalid pointer, always cause a bad > paging fault. Is it's the case, then I think we should do it to reduce > number of failure modes and syzbot reports.
This one in bpf tree fixes it: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=bbeb6e4323dad9b5e0ee9f60c223dd532e2403b1 Despite this one not having a reproducer, I'm pretty certain it's very much related to all the ones coming in yesterday (which the above fixes). >> This bug is generated by a dumb bot. It may contain errors. >> See https://goo.gl/tpsmEJ for details. >> Direct all questions to syzkal...@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 >> 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+unsubscr...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/syzkaller-bugs/001a1140bf605479be05627d75c7%40google.com. >> For more options, visit https://groups.google.com/d/optout.
