From: Aleksandr Nogikh <nogikh@xxxxxxxxxx> 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 patches: 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. 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(). v6: * Revert usage of skb extensions due to potential memory leak. Patch 2/3 is now idential to that in v2. * Patches 1/3 and 3/3 are otherwise identical to v5. v5: https://lore.kernel.org/linux-wireless/20201029173620.2121359-1-aleksandrnogikh@xxxxxxxxx/ * Collecting remote coverate at ieee80211_rx_list() instead of ieee80211_rx() v4: https://lkml.kernel.org/r/20201028182018.1780842-1-aleksandrnogikh@xxxxxxxxx * 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/20201026150851.528148-1-aleksandrnogikh@xxxxxxxxx * kcov_handle is now stored in skb extensions instead of sk_buff itself. * Updated the cover letter. v2: https://lkml.kernel.org/r/20201009170202.103512-1-a.nogikh@xxxxxxxxx * Moved KCOV annotations from ieee80211_tasklet_handler to ieee80211_rx. * Updated kcov_common_handle() to return 0 if it is called in interrupt context. v1: https://lkml.kernel.org/r/20201007101726.3149375-1-a.nogikh@xxxxxxxxx Aleksandr Nogikh (3): kernel: make kcov_common_handle consider the current context net: store KCOV remote handle in sk_buff mac80211: add KCOV remote annotations to incoming frame processing include/linux/skbuff.h | 21 +++++++++++++++++++++ kernel/kcov.c | 2 ++ net/core/skbuff.c | 1 + net/mac80211/iface.c | 2 ++ net/mac80211/rx.c | 16 +++++++++------- 5 files changed, 35 insertions(+), 7 deletions(-) -- 2.29.2.454.gaff20da3a2-goog
