kernel/linux.git/lib/Kconfig.debug, branch v5.15.220

kcov: fix data corruption and race conditions on PREEMPT_RT

2026-09-02T12:27:27+00:00

[ Upstream commit 2eed77fdcb0cc48e8eccb2bcd4b7f2c6d650e84c ] syzbot is reporting KCOV state corruption on PREEMPT_RT kernels, for the temporary storage used for saving/restoring remote KCOV state is currently allocated as the per-CPU area. On PREEMPT_RT kernels, softirq handlers run as preemptible task threads (e.g., ksoftirqd). If a softirq context preempts a task running a remote KCOV session, it safely saves the task's state into the per-CPU area. However, if that softirq thread is subsequently preempted by a higher- priority softirq thread on the same CPU, the second softirq will overwrite the same per-CPU area, permanently destroying the original task's KCOV state. Fix this data corruption by moving the temporary storage from the per-CPU area to the per-thread area. Since each softirq thread now owns its own task context, nested softirq preemption no longer causes data overwrites. Note that while the temporary storage is now on a per-thread basis, the per-CPU kcov_percpu_data.lock must be retained, for we need to ensure that kcov_remote_start() and kcov_remote_stop() operate atomically without racing against asynchronous interrupts that manipulate the current task's KCOV state. It is likely that GFP_KERNEL allocation by vmalloc_node() in kcov_init() has already called panic() before returning NULL, for there will be no OOM-killable userspace processes when __init function of built-in module runs. But this patch also fixes crashing the kernel when vmalloc_node() in kcov_init() returned NULL, for kcov_init() left per-CPU irq_area == NULL but kcov_remote_start() depends on per-CPU irq_area != NULL, resulting in (1) doing vmalloc() in kcov_remote_start() despite !in_task() context (2) out-of-array-bounds access if (1) succeeded but kcov->remote_size < CONFIG_KCOV_IRQ_AREA_SIZE (3) always leak memory allocated by (1), eventually killing all OOM-killable userspace processes problems. Link: https://lore.kernel.org/43552d09-2ce2-4b19-b0d3-a2d1ab952145@I-love.SAKURA.ne.jp Reported-by: syzbot+3f51ad7ac3ae57a6fdcc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3f51ad7ac3ae57a6fdcc Reported-by: syzbot+47cf95ca1f9dcca872c8@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=47cf95ca1f9dcca872c8 Reported-by: syzbot+8a173e13208949931dc7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=8a173e13208949931dc7 Reported-by: syzbot+90984d3713722683112e@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=90984d3713722683112e Analyzed-by: AI Mode in Google Search (no mail address) Fixes: 5ff3b30ab57d ("kcov: collect coverage from interrupts") Signed-off-by: Tetsuo Handa Reviewed-by: Alexander Potapenko Cc: Alan Stern Cc: Andrey Konovalov Cc: Christoph Hellwig Cc: Clark Williams Cc: Dmitry Vyukov Cc: Greg Kroah-Hartman Cc: Marco Elver Cc: Mark Brown Cc: Roman Gushchin Cc: Sebastian Andrzej Siewior Cc: Signed-off-by: Andrew Morton [ Adjusted the `kcov_init()` deletion context to plain `vmalloc()` since 5.15 lacks the `vmalloc_node()`/`cpu_to_node()` conversion. ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

lockdep: Fix upper limit for LOCKDEP_*_BITS configs

2025-03-13T11:50:17+00:00

[ Upstream commit e638072e61726cae363d48812815197a2a0e097f ] Lockdep has a set of configs used to determine the size of the static arrays that it uses. However, the upper limit that was initially setup for these configs is too high (30 bit shift). This equates to several GiB of static memory for individual symbols. Using such high values leads to linker errors: $ make defconfig $ ./scripts/config -e PROVE_LOCKING --set-val LOCKDEP_BITS 30 $ make olddefconfig all [...] ld: kernel image bigger than KERNEL_IMAGE_SIZE ld: section .bss VMA wraps around address space Adjust the upper limits to the maximum values that avoid these issues. The need for anything more, likely points to a problem elsewhere. Note that LOCKDEP_CHAINS_BITS was intentionally left out as its upper limit had a different symptom and has already been fixed [1]. Reported-by: J. R. Okajima Closes: https://lore.kernel.org/all/30795.1620913191@jrobl/ [1] Cc: Peter Zijlstra Cc: Boqun Feng Cc: Ingo Molnar Cc: Waiman Long Cc: Will Deacon Acked-by: Waiman Long Signed-off-by: Carlos Llamas Signed-off-by: Boqun Feng Link: https://lore.kernel.org/r/20241024183631.643450-2-cmllamas@google.com Signed-off-by: Sasha Levin

bpf, kconfig: Fix DEBUG_INFO_BTF_MODULES Kconfig definition

2024-05-17T09:50:46+00:00

[ Upstream commit 229087f6f1dc2d0c38feba805770f28529980ec0 ] Turns out that due to CONFIG_DEBUG_INFO_BTF_MODULES not having an explicitly specified "menu item name" in Kconfig, it's basically impossible to turn it off (see [0]). This patch fixes the issue by defining menu name for CONFIG_DEBUG_INFO_BTF_MODULES, which makes it actually adjustable and independent of CONFIG_DEBUG_INFO_BTF, in the sense that one can have DEBUG_INFO_BTF=y and DEBUG_INFO_BTF_MODULES=n. We still keep it as defaulting to Y, of course. Fixes: 5f9ae91f7c0d ("kbuild: Build kernel module BTFs if BTF is enabled and pahole supports it") Reported-by: Vincent Li Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/CAK3+h2xiFfzQ9UXf56nrRRP=p1+iUxGoEP5B+aq9MDT5jLXDSg@mail.gmail.com [0] Link: https://lore.kernel.org/bpf/20240404220344.3879270-1-andrii@kernel.org Signed-off-by: Sasha Levin

arch: Introduce CONFIG_FUNCTION_ALIGNMENT

2024-04-10T14:18:49+00:00

commit d49a0626216b95cd4bf696f6acf55f39a16ab0bb upstream. Generic function-alignment infrastructure. Architectures can select FUNCTION_ALIGNMENT_xxB symbols; the FUNCTION_ALIGNMENT symbol is then set to the largest such selected size, 0 otherwise. >From this the -falign-functions compiler argument and __ALIGN macro are set. This incorporates the DEBUG_FORCE_FUNCTION_ALIGN_64B knob and future alignment requirements for x86_64 (later in this series) into a single place. NOTE: also removes the 0x90 filler byte from the generic __ALIGN primitive, that value makes no sense outside of x86. NOTE: .balign 0 reverts to a no-op. Requested-by: Linus Torvalds Change-Id: I053b3c408d56988381feb8c8bdb5e27ea221755f Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20220915111143.719248727@infradead.org [cascardo: adjust context at arch/x86/Kconfig] Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman

lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default

2023-10-25T09:58:54+00:00

commit cc6003916ed46d7a67d91ee32de0f9138047d55f upstream. In workloads where this_cpu operations are frequently performed, enabling DEBUG_PREEMPT may result in significant increase in runtime overhead due to frequent invocation of __this_cpu_preempt_check() function. This can be demonstrated through benchmarks such as hackbench where this configuration results in a 10% reduction in performance, primarily due to the added overhead within memcg charging path. Therefore, do not to enable DEBUG_PREEMPT by default and make users aware of its potential impact on performance in some workloads. hackbench-process-sockets debug_preempt no_debug_preempt Amean 1 0.4743 ( 0.00%) 0.4295 * 9.45%* Amean 4 1.4191 ( 0.00%) 1.2650 * 10.86%* Amean 7 2.2677 ( 0.00%) 2.0094 * 11.39%* Amean 12 3.6821 ( 0.00%) 3.2115 * 12.78%* Amean 21 6.6752 ( 0.00%) 5.7956 * 13.18%* Amean 30 9.6646 ( 0.00%) 8.5197 * 11.85%* Amean 48 15.3363 ( 0.00%) 13.5559 * 11.61%* Amean 79 24.8603 ( 0.00%) 22.0597 * 11.27%* Amean 96 30.1240 ( 0.00%) 26.8073 * 11.01%* Link: https://lkml.kernel.org/r/20230121033942.350387-1-42.hyeyoo@gmail.com Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Acked-by: Roman Gushchin Acked-by: Mel Gorman Acked-by: Davidlohr Bueso Cc: Ben Segall Cc: Christoph Lameter Cc: Daniel Bristot de Oliveira Cc: David Rientjes Cc: Dennis Zhou Cc: Dietmar Eggemann Cc: Ingo Molnar Cc: Johannes Weiner Cc: Joonsoo Kim Cc: Juri Lelli Cc: Matthew Wilcox Cc: Muchun Song Cc: Pekka Enberg Cc: Peter Zijlstra Cc: Shakeel Butt Cc: Steven Rostedt (Google) Cc: Tejun Heo Cc: Valentin Schneider Cc: Vincent Guittot Cc: Vlastimil Babka Signed-off-by: Andrew Morton Cc: Luiz Capitulino Signed-off-by: Greg Kroah-Hartman

lib/Kconfig.debug: Allow BTF + DWARF5 with pahole 1.21+

2023-02-25T11:06:46+00:00

commit 42d9b379e3e1790eafb87c799c9edfd0b37a37c7 upstream. Commit 98cd6f521f10 ("Kconfig: allow explicit opt in to DWARF v5") prevented CONFIG_DEBUG_INFO_DWARF5 from being selected when CONFIG_DEBUG_INFO_BTF is enabled because pahole had issues with clang's DWARF5 info. This was resolved by [1], which is in pahole v1.21. Allow DEBUG_INFO_DWARF5 to be selected with DEBUG_INFO_BTF when using pahole v1.21 or newer. [1]: https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=7d8e829f636f47aba2e1b6eda57e74d8e31f733c Signed-off-by: Nathan Chancellor Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20220201205624.652313-6-nathan@kernel.org Signed-off-by: Matthias Maennich Signed-off-by: Greg Kroah-Hartman

lib/Kconfig.debug: Use CONFIG_PAHOLE_VERSION

2023-02-25T11:06:46+00:00

commit 6323c81350b73a4569cf52df85f80273faa64071 upstream. Now that CONFIG_PAHOLE_VERSION exists, use it in the definition of CONFIG_PAHOLE_HAS_SPLIT_BTF and CONFIG_PAHOLE_HAS_BTF_TAG to reduce the amount of duplication across the tree. Signed-off-by: Nathan Chancellor Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20220201205624.652313-5-nathan@kernel.org [maennich: omitted patching non-existing config PAHOLE_HAS_BTF_TAG] Signed-off-by: Matthias Maennich Signed-off-by: Greg Kroah-Hartman

Kconfig.debug: provide a little extra FRAME_WARN leeway when KASAN is enabled

2022-12-08T10:28:44+00:00

[ Upstream commit 152fe65f300e1819d59b80477d3e0999b4d5d7d2 ] When enabled, KASAN enlarges function's stack-frames. Pushing quite a few over the current threshold. This can mainly be seen on 32-bit architectures where the present limit (when !GCC) is a lowly 1024-Bytes. Link: https://lkml.kernel.org/r/20221125120750.3537134-3-lee@kernel.org Signed-off-by: Lee Jones Acked-by: Arnd Bergmann Cc: Alex Deucher Cc: "Christian König" Cc: Daniel Vetter Cc: David Airlie Cc: Harry Wentland Cc: Leo Li Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: "Pan, Xinhui" Cc: Rodrigo Siqueira Cc: Thomas Zimmermann Cc: Tom Rix Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin

parisc: Increase FRAME_WARN to 2048 bytes on parisc

2022-12-08T10:28:44+00:00

[ Upstream commit 8d192bec534bd5b778135769a12e5f04580771f7 ] PA-RISC uses a much bigger frame size for functions than other architectures. So increase it to 2048 for 32- and 64-bit kernels. This fixes e.g. a warning in lib/xxhash.c. Reported-by: kernel test robot Signed-off-by: Helge Deller Stable-dep-of: 152fe65f300e ("Kconfig.debug: provide a little extra FRAME_WARN leeway when KASAN is enabled") Signed-off-by: Sasha Levin

error-injection: Add prompt for function error injection

2022-12-08T10:28:42+00:00

commit a4412fdd49dc011bcc2c0d81ac4cab7457092650 upstream. The config to be able to inject error codes into any function annotated with ALLOW_ERROR_INJECTION() is enabled when FUNCTION_ERROR_INJECTION is enabled. But unfortunately, this is always enabled on x86 when KPROBES is enabled, and there's no way to turn it off. As kprobes is useful for observability of the kernel, it is useful to have it enabled in production environments. But error injection should be avoided. Add a prompt to the config to allow it to be disabled even when kprobes is enabled, and get rid of the "def_bool y". This is a kernel debug feature (it's in Kconfig.debug), and should have never been something enabled by default. Cc: stable@vger.kernel.org Fixes: 540adea3809f6 ("error-injection: Separate error-injection from kprobe") Signed-off-by: Steven Rostedt (Google) Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman