On Thu, Feb 15, 2018 at 11:31 AM, Guillaume Nault <g.na...@alphalink.fr> wrote: > On Thu, Feb 15, 2018 at 06:01:16PM +0200, Denys Fedoryshchenko wrote: >> On 2018-02-15 17:55, Guillaume Nault wrote: >> > On Thu, Feb 15, 2018 at 12:19:52PM +0200, Denys Fedoryshchenko wrote: >> > > 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] >> > >> > Your first guess was right. It looks like we have an issue with >> > reference counting on the channels. Can you send me your ppp_generic.o? >> http://nuclearcat.com/ppp_generic.o >> Compiled with gcc version 6.4.0 (Gentoo 6.4.0-r1 p1.3) >> > From what I can see, ppp_release() and ioctl(PPPIOCCONNECT) are called > concurrently on the same ppp_file. Even if this ppp_file was pointed at > by two different file descriptors, I can't see how this could defeat > the reference counting mechanism. I'm going to think more about it.
For me it looks like pch->clist is not removed from the list ppp->channels when destroyed via ppp_release(). But I don't want to pretend I understand ppp logic.