[Bug 1699161] Re: lshw crashes with SEGV in privileged containers

[Eric Desrochers]

### VERIFICATION ARTFUL ###

* With current artful-updates package.
root at privlshwA:~# dpkg -l | grep -i lshw
ii  lshw          02.18-0.1ubuntu3  amd64        information about hardware configuration


root at privlshwA:~# lshw
Segmentation fault (core dumped)


* With current artful-proposed package.

root at privlshwA:~# dpkg -l | grep -i lshw
ii  lshw          02.18-0.1ubuntu4  amd64        information about hardware configuration


root at privlshwA:~# lshw
...
        *-usb
             description: USB controller
             product: Sunrise Point-LP USB 3.0 xHCI Controller
             vendor: Intel Corporation
             physical id: 14
             bus info: pci at 0000:00:14.0
             version: 21
             width: 64 bits
             clock: 33MHz
             capabilities: pm msi xhci bus_master cap_list
             configuration: driver=xhci_hcd latency=0
             resources: irq:120 memory:ec120000-ec12ffff
...

** Tags removed: verification-needed-artful
** Tags added: verification-done-artful

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https://bugs.launchpad.net/bugs/1699161

Title:
  lshw crashes with SEGV in privileged containers

Status in lshw package in Ubuntu:
  In Progress
Status in lshw source package in Xenial:
  Confirmed
Status in lshw source package in Zesty:
  Fix Committed
Status in lshw source package in Artful:
  Fix Committed
Status in lshw source package in Bionic:
  In Progress
Status in lshw package in Debian:
  New

Bug description:
  [Impact]

   * lshw crashes with SEGV in privileged containers, unless you disable
  the 'usb' test: $ lshw -disable usb

  [Test Case]

  ## Create a privileged container. ##
  $ lxc launch ubuntu:16.04 priv -c security.privileged=true
  Creating priv
  Starting priv

  ## Execute lshw inside the privileged container. ##
  $ lxc exec priv bash
  root at priv:~#

  root at priv:~#lshw
  Segmentation fault

  [Regression Potential]

   * Risks of regression are low.

   * I have tested lshw inside containers (unprivileges/privileges) and
  baremetal with success connecting different types of usb device :
  webcam, usb keys, ... The usb output of lshw cmd is shown as expected,
  but this time without segfaulting when container in privilege mode.

   * Basically, the code look if both files doesn't exists

  #define PROCBUSUSBDEVICES "/proc/bus/usb/devices"
  #define SYSKERNELDEBUGUSBDEVICES "/sys/kernel/debug/usb/devices"
  ...
    if (!exists(SYSKERNELDEBUGUSBDEVICES) && !exists(PROCBUSUSBDEVICES))
  __return false;

  I kept the above in place.

  But what if only 1 of the 2 files exists ?

  For that reason I added an extra verification if
  SYSKERNELDEBUGUSBDEVICES exist -> fopen SYSKERNELDEBUGUSBDEVICES.

  and

  if fopen SYSKERNELDEBUGUSBDEVICES fails and PROCBUSUSBDEVICES exist
  then -> fopen "PROCBUSUSBDEVICES"

  The code first look for SYSKERNELDEBUGUSBDEVICES and if it fails it
  jump to PROCBUSUSBDEVICES.

  But if PROCBUSUSBDEVICES fails there was no mechanism to skip, thus
  segfault.

  I also added another if statement in case PROCBUSUSBDEVICES fails like
  in this situation (no such file or directory) in privileged container,
  same as if SYSKERNELDEBUGUSBDEVICES can't be opened to force to jump
  on trying PROCBUSUSBDEVICES.

  [Other Info]

   * PR :
     https://ezix.org/src/pkg/lshw/pulls/9

   * Upstream Commit:
     https://ezix.org/src/pkg/lshw/commit/7b99d35064230f908551ba65c29264d90f49f246

   * This bug doesn't affect Trusty in privileged container. (The code
  is a bit different in Trusty/lshw package. It basically doesn't rely
  on SYSKERNELDEBUGUSBDEVICES, meaning that it is only validating if
  PROCBUSUSBDEVICES exist or not and react accordingly).

   * Only affect Xenial and late.

   * The bug has been introduced upstream after this specific commit :
     https://ezix.org/src/pkg/lshw/commit/9f05be36f7ce6117731e312053d1ec91348a3051

  * This particular bug isn't reproducible in Debian (tested with sid in
  privileged mode) container image because both files doesn't exist in
  their image, thus making the lshw stop here :

    if (!exists(SYSKERNELDEBUGUSBDEVICES) && !exists(PROCBUSUSBDEVICES))
    return false;

  With that being said, I filed a debian bug anyway mentioning that it would be great for them to merge the upstream PR since Ubuntu is merging/syncing from them, and it won't hurt debian lshw package, if they change or not their image behavior one day. Even if not necessary fixing an actual debian/lshw bug.
  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=878792

  ** Discussion with apw on #ubuntu-release **
  [10:45:45] <apw> slashd, artful is open for SRUs, when BB opens it will start from whatever is in A
  [11:13:49] <apw> -propsoed gets copied to bb-proposed too yes

  [Original Description]
  When running lshw in a Xenial container, I'm getting a segmentation fault. I'll attach the apport crash dump.

  ```
  stgraber at castiana:~$ lxc launch ubuntu:16.04 priv -c security.privileged=true
  Creating priv
  Starting priv

  stgraber at castiana:~$ lxc exec priv bash
  root at priv:~# lshw
  Segmentation fault
  root at priv:~#
  ```

  [strace of lshw]
  open("/usr/share/hwdata/usb.ids", O_RDONLY) = -1 ENOENT (No such file or directory)
  open("/etc/usb.ids", O_RDONLY)          = -1 ENOENT (No such file or directory)
  open("/usr/share/usb.ids", O_RDONLY)    = -1 ENOENT (No such file or directory)
  open("/usr/local/share/usb.ids", O_RDONLY) = -1 ENOENT (No such file or directory)
  open("/usr/share/lshw-common/usb.ids", O_RDONLY) = -1 ENOENT (No such file or directory)
  open("/usr/share/usb.ids", O_RDONLY)    = -1 ENOENT (No such file or directory)
  open("/sys/kernel/debug/usb/devices", O_RDONLY) = -1 EACCES (Permission denied)
  open("/proc/bus/usb/devices", O_RDONLY) = -1 ENOENT (No such file or directory)
  --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0} ---
  +++ killed by SIGSEGV +++
  Segmentation fault

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