| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20210307040142.GA2930@b29397-desktop>
Date: Sun, 7 Mar 2021 12:01:42 +0800
From: Peter Chen <peter.chen@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Pawel Laszczak <pawell@...ence.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Jacob Wen <jian.w.wen@...cle.com>,
Felipe Balbi <balbi@...nel.org>,
Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 0/2] tracing: Detect unsafe dereferencing of pointers
from trace events
On 21-03-02 09:56:05, Steven Rostedt wrote:
> On Tue, 2 Mar 2021 16:23:55 +0800
> Peter Chen <peter.chen@...nel.org> wrote:
>
> s it looks like it uses %pa which IIUC from the printk code, it
> > > >> dereferences the pointer to find it's virtual address. The event has
> > > >> this as the field:
> > > >>
> > > >> __field(struct cdns3_trb *, start_trb_addr)
> > > >>
> > > >> Assigns it with:
> > > >>
> > > >> __entry->start_trb_addr = req->trb;
> > > >>
> > > >> And prints that with %pa, which will dereference pointer at the time of
> > > >> reading, where the address in question may no longer be around. That
> > > >> looks to me as a potential bug.
> >
> > Steven, thanks for reporting. Do you mind sending patch to fix it?
> > If you have no time to do it, I will do it later.
> >
>
> I would have already fixed it, but I wasn't exactly sure how this is used.
>
> In Documentation/core-api/printk-formats.rst we have:
>
> Physical address types phys_addr_t
> ----------------------------------
>
> ::
>
> %pa[p] 0x01234567 or 0x0123456789abcdef
>
> For printing a phys_addr_t type (and its derivatives, such as
> resource_size_t) which can vary based on build options, regardless of the
> width of the CPU data path.
>
> So it only looks like it is used to for the size of the pointer.
>
> I guess something like this might work:
>
> diff --git a/drivers/usb/cdns3/cdns3-trace.h b/drivers/usb/cdns3/cdns3-trace.h
> index 8648c7a7a9dd..d3b8624fc427 100644
> --- a/drivers/usb/cdns3/cdns3-trace.h
> +++ b/drivers/usb/cdns3/cdns3-trace.h
> @@ -214,7 +214,7 @@ DECLARE_EVENT_CLASS(cdns3_log_request,
> __field(int, no_interrupt)
> __field(int, start_trb)
> __field(int, end_trb)
> - __field(struct cdns3_trb *, start_trb_addr)
> + __field(phys_addr_t, start_trb_addr)
> __field(int, flags)
> __field(unsigned int, stream_id)
> ),
> @@ -230,7 +230,7 @@ DECLARE_EVENT_CLASS(cdns3_log_request,
> __entry->no_interrupt = req->request.no_interrupt;
> __entry->start_trb = req->start_trb;
> __entry->end_trb = req->end_trb;
> - __entry->start_trb_addr = req->trb;
> + __entry->start_trb_addr = *(const phys_addr_t *)req->trb;
> __entry->flags = req->flags;
> __entry->stream_id = req->request.stream_id;
> ),
> @@ -244,7 +244,7 @@ DECLARE_EVENT_CLASS(cdns3_log_request,
> __entry->status,
> __entry->start_trb,
> __entry->end_trb,
> - __entry->start_trb_addr,
> + /* %pa dereferences */ &__entry->start_trb_addr,
> __entry->flags,
> __entry->stream_id
> )
>
>
> Can you please test it? I don't have the hardware, but I also want to make
> sure I don't break anything.
>
> Thanks,
>
Since the virtual address for req->trb is NULL before using it. It will
trigger below oops using your change. There is already index
(start_trb/end_trb) for which TRB it has handled, it is not necessary
to trace information for its physical address. I decide to delete this
trace entry, thanks for reporting it.
[ 61.695160] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[ 61.704066] Mem abort info:
[ 61.706910] ESR = 0x96000006
[ 61.710000] EC = 0x25: DABT (current EL), IL = 32 bits
[ 61.715339] SET = 0, FnV = 0
[ 61.718416] EA = 0, S1PTW = 0
[ 61.721575] Data abort info:
[ 61.724482] ISV = 0, ISS = 0x00000006
[ 61.728323] CM = 0, WnR = 0
[ 61.731324] user pgtable: 4k pages, 48-bit VAs, pgdp=00000008856dd000
[ 61.737816] [0000000000000000] pgd=000000088577a003, p4d=000000088577a003, pud=000000088477c003, pmd=0000000000000000
[ 61.748532] Internal error: Oops: 96000006 [#1] PREEMPT SMP
[ 61.754113] Modules linked in: fsl_jr_uio caam_jr caamkeyblob_desc caamhash_desc caamalg_desc crypto_engine rng_core authenc libdes crct10dif_ce mxc_jpeg_encdec imx8_media_dev(C) caam error
Message from syslogd@...8qmmek at Fri Jul 10 06:52:44 2020 ...
imx8qmmek kernel: [ 61.748532] Internal error: Oops: 96000006 [#1] PREEMPT SMP
[ 61.784245] CPU: 3 PID: 188 Comm: 1-0050 Tainted: G C 5.10.0-rc7-04451-gfcfe23a5424-dirty #3
[ 61.793993] Hardware name: Freescale i.MX8QXP MEK (DT)
[ 61.799139] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--)
[ 61.805162] pc : trace_event_raw_event_cdns3_log_request+0xf4/0x170
[ 61.811440] lr : trace_event_raw_event_cdns3_log_request+0x94/0x170
[ 61.817707] sp : ffff80001387ba40
[ 61.821019] x29: ffff80001387ba40 x28: 0000000000000002
[ 61.826336] x27: ffff000801e20080 x26: ffff000800e5c8c8
[ 61.831652] x25: ffff0008044e0c00 x24: ffff000800505308
[ 61.836969] x23: ffff800012464000 x22: 0000000000040050
[ 61.842286] x21: ffff000801e0aa00 x20: ffff0008002e7f18
[ 61.847603] x19: ffff000805131300 x18: 0000000000000000
[ 61.852919] x17: 0000000000000000 x16: 0000000000000000
[ 61.858245] x15: ffff00080081ca78 x14: ffffffffffffffff
[ 61.863570] x13: ffff800012404778 x12: 0000000000000018
[ 61.868896] x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f
[ 61.874213] x9 : fefefefeff2f6f64 x8 : ffffffffffffffff
[ 61.879529] x7 : ffff8000122b05b8 x6 : 0000000000000001
[ 61.884846] x5 : 0000000000000020 x4 : 0000000000000000
[ 61.890163] x3 : 0000000000000000 x2 : 0000000000000004
[ 61.895479] x1 : 0000000000000000 x0 : ffff80001387ba70
[ 61.900806] Call trace:
[ 61.903260] trace_event_raw_event_cdns3_log_request+0xf4/0x170
[ 61.909183] __traceiter_cdns3_free_request+0x34/0x50
[ 61.914241] cdns3_gadget_ep_free_request+0xa8/0xd8
[ 61.919123] usb_ep_free_request+0x34/0xd8
[ 61.923223] composite_dev_cleanup+0xd0/0x170
[ 61.927583] configfs_composite_unbind+0x68/0xa0
[ 61.932205] usb_gadget_remove_driver+0x4c/0xd0
[ 61.936737] usb_del_gadget+0x6c/0xc8
[ 61.940404] cdns3_gadget_exit+0x4c/0x120
[ 61.944420] cdns3_role_stop+0x60/0x90
[ 61.948174] cdns3_role_set+0x64/0xe0
[ 61.951841] usb_role_switch_set_role.part.0+0x3c/0x90
[ 61.956984] usb_role_switch_set_role+0x20/0x30
[ 61.961519] tcpm_mux_set+0x60/0x80
[ 61.965008] tcpm_reset_port+0xa4/0x108
[ 61.968851] tcpm_detach+0x6c/0xa0
[ 61.972256] tcpm_state_machine_work+0x13e0/0x24a0
[ 61.977052] kthread_worker_fn+0x9c/0x168
[ 61.981064] kthread+0x148/0x168
[ 61.984296] ret_from_fork+0x10/0x18
[ 61.987881] Code: b9003a81 b9407661 b9003e81 f9403661 (f9400021)
[ 61.993983] ---[ end trace c8f1af57d3c61281 ]---
[ 61.998669] note: 1-0050[188] exited with preempt_count 2
--
Thanks,
Peter Chen
Powered by blists - more mailing lists