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Date: Thu, 15 Feb 2018 12:19:52 +0200 From: Denys Fedoryshchenko <nuclearcat@...learcat.com> To: Guillaume Nault <g.nault@...halink.fr> Cc: Linux Kernel Network Developers <netdev@...r.kernel.org> Subject: Re: ppp/pppoe, still panic 4.15.3 in ppp_push On 2018-02-14 19:25, Guillaume Nault wrote: > On Wed, Feb 14, 2018 at 06:49:19PM +0200, Denys Fedoryshchenko wrote: >> On 2018-02-14 18:47, Guillaume Nault wrote: >> > On Wed, Feb 14, 2018 at 06:29:34PM +0200, Denys Fedoryshchenko wrote: >> > > On 2018-02-14 18:07, Guillaume Nault wrote: >> > > > On Wed, Feb 14, 2018 at 03:17:23PM +0200, Denys Fedoryshchenko wrote: >> > > > > Hi, >> > > > > >> > > > > Upgraded kernel to 4.15.3, still it crashes after while (several >> > > > > hours, >> > > > > cannot do bisect, as it is production server). >> > > > > >> > > > > dev ppp # gdb ppp_generic.o >> > > > > GNU gdb (Gentoo 7.12.1 vanilla) 7.12.1 >> > > > > <<skipped>> >> > > > > Reading symbols from ppp_generic.o...done. >> > > > > (gdb) list *ppp_push+0x73 >> > > > > 0x681 is in ppp_push (drivers/net/ppp/ppp_generic.c:1663). >> > > > > 1658 list = list->next; >> > > > > 1659 pch = list_entry(list, struct channel, clist); >> > > > > 1660 >> > > > > 1661 spin_lock(&pch->downl); >> > > > > 1662 if (pch->chan) { >> > > > > 1663 if (pch->chan->ops->start_xmit(pch->chan, skb)) >> > > > > 1664 ppp->xmit_pending = NULL; >> > > > > 1665 } else { >> > > > > 1666 /* channel got unregistered */ >> > > > > 1667 kfree_skb(skb); >> > > > > >> > > > > >> > > > I expect a memory corruption. Do you have the possibility to run with >> > > > KASAN by any chance? >> > > I will try to enable it tonight. For now i reverted "drivers, net, >> > > ppp: >> > > convert ppp_file.refcnt from atomic_t to refcount_t" for test. >> > > >> > This commit looks good to me. Do you have doubts about it because it's >> > new in 4.15? Does it mean that your last known-good kernel is 4.14? >> >> I am just doing "manual" bisect, checking all possibilities, and >> picking >> patch to revert randomly. >> > Must be a painful process. Are all of your networking modules required? > With luck, you might be able to isolate a faulty module in fewer steps. > >> Yes, correct, my known-good is 4.14.2. >> > Good to know. > > Let me know if you can get a KASAN trace. Here we go: <srv> [24558.921549] ================================================================== <srv> [24558.922167] BUG: KASAN: use-after-free in ppp_ioctl+0xa6a/0x1522 [ppp_generic] <srv> [24558.922776] Write of size 8 at addr ffff8803d35bf3f8 by task accel-pppd/12622 <srv> [24558.923113] <srv> [24558.923451] CPU: 0 PID: 12622 Comm: accel-pppd Tainted: G W 4.15.3-build-0134 #1 <srv> [24558.924058] Hardware name: HP ProLiant DL320e Gen8 v2, BIOS P80 04/02/2015 <srv> [24558.924406] Call Trace: <srv> [24558.924753] dump_stack+0x46/0x59 <srv> [24558.925103] print_address_description+0x6b/0x23b <srv> [24558.925451] ? ppp_ioctl+0xa6a/0x1522 [ppp_generic] <srv> [24558.925797] kasan_report+0x21b/0x241 <srv> [24558.926136] ppp_ioctl+0xa6a/0x1522 [ppp_generic] <srv> [24558.926479] ? ppp_nl_newlink+0x1da/0x1da [ppp_generic] <srv> [24558.926829] ? sock_sendmsg+0x89/0x99 <srv> [24558.927176] ? __vfs_write+0xd9/0x4ad <srv> [24558.927523] ? kernel_read+0xed/0xed <srv> [24558.927872] ? SyS_getpeername+0x18c/0x18c <srv> [24558.928213] ? bit_waitqueue+0x2a/0x2a <srv> [24558.928561] ? wake_atomic_t_function+0x115/0x115 <srv> [24558.928898] vfs_ioctl+0x6e/0x81 <srv> [24558.929228] do_vfs_ioctl+0xa00/0xb10 <srv> [24558.929571] ? sigprocmask+0x1a6/0x1d0 <srv> [24558.929907] ? sigsuspend+0x13e/0x13e <srv> [24558.930239] ? ioctl_preallocate+0x14e/0x14e <srv> [24558.930568] ? SyS_rt_sigprocmask+0xf1/0x142 <srv> [24558.930904] ? sigprocmask+0x1d0/0x1d0 <srv> [24558.931252] SyS_ioctl+0x39/0x55 <srv> [24558.931595] ? do_vfs_ioctl+0xb10/0xb10 <srv> [24558.931942] do_syscall_64+0x1b1/0x31f <srv> [24558.932288] entry_SYSCALL_64_after_hwframe+0x21/0x86 <srv> [24558.932627] RIP: 0033:0x7f302849d8a7 <srv> [24558.932965] RSP: 002b:00007f3029a52af8 EFLAGS: 00000206 ORIG_RAX: 0000000000000010 <srv> [24558.933578] RAX: ffffffffffffffda RBX: 00007f3027d861e3 RCX: 00007f302849d8a7 <srv> [24558.933927] RDX: 00007f3023f49468 RSI: 000000004004743a RDI: 0000000000003a67 <srv> [24558.934266] RBP: 00007f3029a52b20 R08: 0000000000000000 R09: 000055c8308d8e40 <srv> [24558.934607] R10: 0000000000000008 R11: 0000000000000206 R12: 00007f3023f49358 <srv> [24558.934947] R13: 00007ffe86e5723f R14: 0000000000000000 R15: 00007f3029a53700 <srv> [24558.935288] <srv> [24558.935626] Allocated by task 12622: <srv> [24558.935972] ppp_register_net_channel+0x5f/0x5c6 [ppp_generic] <srv> [24558.936306] pppoe_connect+0xab7/0xc71 [pppoe] <srv> [24558.936640] SyS_connect+0x14b/0x1b7 <srv> [24558.936975] do_syscall_64+0x1b1/0x31f <srv> [24558.937319] entry_SYSCALL_64_after_hwframe+0x21/0x86 <srv> [24558.937655] <srv> [24558.937993] Freed by task 12622: <srv> [24558.938321] kfree+0xb0/0x11d <srv> [24558.938658] ppp_release+0x111/0x120 [ppp_generic] <srv> [24558.938994] __fput+0x2ba/0x51a <srv> [24558.939332] task_work_run+0x11c/0x13d <srv> [24558.939676] exit_to_usermode_loop+0x7c/0xaf <srv> [24558.940022] do_syscall_64+0x2ea/0x31f <srv> [24558.940368] entry_SYSCALL_64_after_hwframe+0x21/0x86 <srv> [24558.947099] <srv> [24558.947443] The buggy address belongs to the object at ffff8803d35bf340 [24558.947443] which belongs to the cache kmalloc-256 of size 256 <srv> [24558.948064] The buggy address is located 184 bytes inside of [24558.948064] 256-byte region [ffff8803d35bf340, ffff8803d35bf440) <srv> [24558.948676] The buggy address belongs to the page: <srv> [24558.949019] page:ffffea000f4d6f00 count:1 mapcount:0 mapping: (null) index:0xffff8803d35bfc00 compound_mapcount: 0 <srv> [24558.949633] flags: 0x17ffe00000008100(slab|head) <srv> [24558.949980] raw: 17ffe00000008100 0000000000000000 ffff8803d35bfc00 000000010033002e <srv> [24558.950597] raw: ffffea000d98c020 ffffea000df57d20 ffff8803f1c0f480 0000000000000000 <srv> [24558.951209] page dumped because: kasan: bad access detected <srv> [24558.951546] <srv> [24558.951880] Memory state around the buggy address: <srv> [24558.952217] ffff8803d35bf280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb <srv> [24558.952818] ffff8803d35bf300: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb <srv> [24558.953415] >ffff8803d35bf380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb <srv> [24558.954021] ^ <srv> [24558.954365] ffff8803d35bf400: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc <srv> [24558.954969] ffff8803d35bf480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 <srv> [24558.955572] ================================================================== <srv> [24558.956169] Disabling lock debugging due to kernel taint
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