Messages in this thread | | | Subject | Re: KASAN: use-after-free Read in l2tp_session_create | From | James Chapman <> | Date | Fri, 20 Jul 2018 08:53:04 +0100 |
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On 18/07/18 12:00, Dmitry Vyukov wrote: > On Tue, Jan 16, 2018 at 7:29 PM, syzbot > <syzbot+065d0fc357520c8f6039@syzkaller.appspotmail.com> wrote: >> Hello, >> >> syzkaller hit the following crash on >> a8750ddca918032d6349adbf9a4b6555e7db20da >> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.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+065d0fc357520c8f6039@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. > > James, > > Did you fix this? You asked syzbot to test a fix for this bug some time ago. > If yes, did you include the Reported-by tag in the commit? This bug is > still considered open by syzbot. But it stopped happening ~4 months > ago:
Yes, I think this has been fixed now. I think it was fixed by Guillaume's 6b9f34239b00e6956a267abed2bc559ede556ad6 that was actually to fix another syzbot bug fbeeb5c3b538e8545644 which looks similar to this one.
> https://syzkaller.appspot.com/bug?id=6fed0854381422329e78d7e16fb9cf4af8c9aef1 > We are also seeing these crashes in 4.4 and 4.9, it would be good to > backport the fix.
It looks like 6b9f34239b00e6956a267abed2bc559ede556ad6 hasn't made it to 4.9 or 4.4.
> > Thanks > > >> ================================================================== >> BUG: KASAN: use-after-free in l2tp_session_create+0xa6d/0xc60 >> net/l2tp/l2tp_core.c:1757 >> Read of size 4 at addr ffff8801d80ad868 by task syz-executor3/5462 >> >> CPU: 0 PID: 5462 Comm: syz-executor3 Not tainted 4.15.0-rc8+ #263 >> 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:252 >> kasan_report_error mm/kasan/report.c:351 [inline] >> kasan_report+0x25b/0x340 mm/kasan/report.c:409 >> __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429 >> l2tp_session_create+0xa6d/0xc60 net/l2tp/l2tp_core.c:1757 >> pppol2tp_connect+0xed7/0x1dd0 net/l2tp/l2tp_ppp.c:748 >> SYSC_connect+0x213/0x4a0 net/socket.c:1621 >> SyS_connect+0x24/0x30 net/socket.c:1602 >> entry_SYSCALL_64_fastpath+0x29/0xa0 >> RIP: 0033:0x452df9 >> RSP: 002b:00007f93ec47fc58 EFLAGS: 00000212 ORIG_RAX: 000000000000002a >> RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452df9 >> RDX: 000000000000002e RSI: 00000000205fafd2 RDI: 0000000000000018 >> RBP: 00000000000005a9 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f6878 >> R13: 00000000ffffffff R14: 00007f93ec4806d4 R15: 0000000000000000 >> >> Allocated by task 5462: >> 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:551 >> kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610 >> kmalloc include/linux/slab.h:499 [inline] >> kzalloc include/linux/slab.h:688 [inline] >> l2tp_tunnel_create+0x5e1/0x17f0 net/l2tp/l2tp_core.c:1554 >> pppol2tp_connect+0x14b7/0x1dd0 net/l2tp/l2tp_ppp.c:707 >> SYSC_connect+0x213/0x4a0 net/socket.c:1621 >> SyS_connect+0x24/0x30 net/socket.c:1602 >> entry_SYSCALL_64_fastpath+0x29/0xa0 >> >> Freed by task 5484: >> save_stack+0x43/0xd0 mm/kasan/kasan.c:447 >> set_track mm/kasan/kasan.c:459 [inline] >> kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 >> __cache_free mm/slab.c:3488 [inline] >> kfree+0xd6/0x260 mm/slab.c:3803 >> __rcu_reclaim kernel/rcu/rcu.h:190 [inline] >> rcu_do_batch kernel/rcu/tree.c:2758 [inline] >> invoke_rcu_callbacks kernel/rcu/tree.c:3012 [inline] >> __rcu_process_callbacks kernel/rcu/tree.c:2979 [inline] >> rcu_process_callbacks+0xe94/0x17f0 kernel/rcu/tree.c:2996 >> __do_softirq+0x2d7/0xb85 kernel/softirq.c:285 >> >> The buggy address belongs to the object at ffff8801d80ad780 >> which belongs to the cache kmalloc-512 of size 512 >> The buggy address is located 232 bytes inside of >> 512-byte region [ffff8801d80ad780, ffff8801d80ad980) >> The buggy address belongs to the page: >> page:ffffea0007602b40 count:1 mapcount:0 mapping:ffff8801d80ad000 index:0x0 >> flags: 0x2fffc0000000100(slab) >> raw: 02fffc0000000100 ffff8801d80ad000 0000000000000000 0000000100000006 >> raw: ffffea00070e8760 ffffea00070f8ca0 ffff8801dac00940 0000000000000000 >> page dumped because: kasan: bad access detected >> >> Memory state around the buggy address: >> ffff8801d80ad700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> ffff8801d80ad780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>> ffff8801d80ad800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ^ >> ffff8801d80ad880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ffff8801d80ad900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ================================================================== >> >> >> --- >> 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 >> 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/001a11405130a984300562e8e7b3%40google.com. >> For more options, visit https://groups.google.com/d/optout.
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