[v5,0/3] net, mac80211, kernel: enable KCOV remote coverage collection for 802.11 frame handling

Message

Aleksandr Nogikh Oct. 29, 2020, 5:36 p.m. UTC

From: Aleksandr Nogikh <[e-mail]>

This patch series enables remote KCOV coverage collection during
802.11 frames processing. These changes make it possible to perform
coverage-guided fuzzing in search of remotely triggerable bugs.

Normally, KCOV collects coverage information for the code that is
executed inside the system call context. It is easy to identify where
that coverage should go and whether it should be collected at all by
looking at the current process. If KCOV was enabled on that process,
coverage will be stored in a buffer specific to that process.
Howerever, it is not always enough as handling can happen elsewhere
(e.g. in separate kernel threads).

When it is impossible to infer KCOV-related info just by looking at
the currently running process, one needs to manually pass some
information to the code that should be instrumented. The information
takes the form of 64 bit integers (KCOV remote handles). Zero is the
special value that corresponds to an empty handle. More details on
KCOV and remote coverage collection can be found in
Documentation/dev-tools/kcov.rst.

The series consists of three commits.
1. Apply a minor fix to kcov_common_handle() so that it returns a
valid handle (zero) when called in an interrupt context.
2. Take the remote handle from KCOV and attach it to newly allocated
SKBs as an skb extension. If the allocation happens inside a system
call context, the SKB will be tied to the process that issued the
syscall (if that process is interested in remote coverage collection).
3. Annotate the code that processes incoming 802.11 frames with
kcov_remote_start()/kcov_remote_stop().

v5:
* Collecting remote coverate at ieee80211_rx_list() instead of
  ieee80211_rx()

v4:
https://lkml.kernel.org/r/[e-mail]
* CONFIG_SKB_EXTENSIONS is now automatically selected by CONFIG_KCOV.
* Elaborated on a minor optimization in skb_set_kcov_handle().

v3:
https://lkml.kernel.org/r/[e-mail]
* kcov_handle is now stored in skb extensions instead of sk_buff
  itself.
* Updated the cover letter.

v2:
https://lkml.kernel.org/r/[e-mail]
* Moved KCOV annotations from ieee80211_tasklet_handler to
  ieee80211_rx.
* Updated kcov_common_handle() to return 0 if it is called in
  interrupt context.
* Updated the cover letter.

v1:
https://lkml.kernel.org/r/[e-mail]

Aleksandr Nogikh (3):
  kernel: make kcov_common_handle consider the current context
  net: add kcov handle to skb extensions
  mac80211: add KCOV remote annotations to incoming frame processing

 include/linux/skbuff.h | 36 ++++++++++++++++++++++++++++++++++++
 kernel/kcov.c          |  2 ++
 lib/Kconfig.debug      |  1 +
 net/core/skbuff.c      | 11 +++++++++++
 net/mac80211/iface.c   |  2 ++
 net/mac80211/rx.c      | 16 +++++++++-------
 6 files changed, 61 insertions(+), 7 deletions(-)


base-commit: 3f267ec60b922eff2a5c90d532357a39f155b730

Comments

Jakub Kicinski Nov. 3, 2020, 3 a.m. UTC | #1

On Thu, 29 Oct 2020 17:36:17 +0000 Aleksandr Nogikh wrote:
> From: Aleksandr Nogikh <[e-mail]>
> 
> This patch series enables remote KCOV coverage collection during
> 802.11 frames processing. These changes make it possible to perform
> coverage-guided fuzzing in search of remotely triggerable bugs.
> 
> Normally, KCOV collects coverage information for the code that is
> executed inside the system call context. It is easy to identify where
> that coverage should go and whether it should be collected at all by
> looking at the current process. If KCOV was enabled on that process,
> coverage will be stored in a buffer specific to that process.
> Howerever, it is not always enough as handling can happen elsewhere
> (e.g. in separate kernel threads).
> 
> When it is impossible to infer KCOV-related info just by looking at
> the currently running process, one needs to manually pass some
> information to the code that should be instrumented. The information
> takes the form of 64 bit integers (KCOV remote handles). Zero is the
> special value that corresponds to an empty handle. More details on
> KCOV and remote coverage collection can be found in
> Documentation/dev-tools/kcov.rst.
> 
> The series consists of three commits.
> 1. Apply a minor fix to kcov_common_handle() so that it returns a
> valid handle (zero) when called in an interrupt context.
> 2. Take the remote handle from KCOV and attach it to newly allocated
> SKBs as an skb extension. If the allocation happens inside a system
> call context, the SKB will be tied to the process that issued the
> syscall (if that process is interested in remote coverage collection).
> 3. Annotate the code that processes incoming 802.11 frames with
> kcov_remote_start()/kcov_remote_stop().

Applied, thanks.