On 2018-02-15 21:31, Guillaume Nault 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.
Can you test with CONFIG_REFCOUNT_FULL? (and keep
d780cd44e3ce ("drivers, net, ppp: convert ppp_file.refcnt from
atomic_t to refcount_t")).
Ok, i will try that tonight. On vanilla kernel or reversing mentioned in
previous email patch?
