- Linux-kselftest-mirror - lists.linaro.org

[PATCH v3 bpf-next] selftests/bpf: Fix arena_spin_lock selftest failure

by Saket Kumar Bhaskar

For systems having CONFIG_NR_CPUS set to > 1024 in kernel config the selftest fails as arena_spin_lock_irqsave() returns EOPNOTSUPP. (eg - incase of powerpc default value for CONFIG_NR_CPUS is 8192) The selftest is skipped incase bpf program returns EOPNOTSUPP, with a descriptive message logged. Tested-by: Venkat Rao Bagalkote <venkat88(a)linux.ibm.com> Signed-off-by: Saket Kumar Bhaskar <skb99(a)linux.ibm.com> --- Changes since v2: * Separated arena_spin_lock selftest fix patch from the arena patchset as it has to go via bpf-next tree. * For EOPNOTSUPP set test_skip to 3, to differentiate it from scenarios when run conditions are not met as suggested by Hari. * Tweaked message displayed on SKIP to remove display of online cpus. v2:https://lore.kernel.org/all/20250829165135.1273071-1-skb99@linux.ibm.com/ Changes since v1: Addressed comments from Alexei: * Removed skel->rodata->nr_cpus = get_nprocs() and its usage to get currently online cpus(as it needs to be updated from userspace). v1:https://lore.kernel.org/all/20250805062747.3479221-1-skb99@linux.ibm.com/ --- .../selftests/bpf/prog_tests/arena_spin_lock.c | 13 +++++++++++++ tools/testing/selftests/bpf/progs/arena_spin_lock.c | 5 ++++- 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c b/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c index 0223fce4db2b..693fd86fbde6 100644 --- a/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c +++ b/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c @@ -40,8 +40,13 @@ static void *spin_lock_thread(void *arg) err = bpf_prog_test_run_opts(prog_fd, &topts); ASSERT_OK(err, "test_run err"); + + if (topts.retval == -EOPNOTSUPP) + goto end; + ASSERT_EQ((int)topts.retval, 0, "test_run retval"); +end: pthread_exit(arg); } @@ -63,6 +68,7 @@ static void test_arena_spin_lock_size(int size) skel = arena_spin_lock__open_and_load(); if (!ASSERT_OK_PTR(skel, "arena_spin_lock__open_and_load")) return; + if (skel->data->test_skip == 2) { test__skip(); goto end; @@ -86,6 +92,13 @@ static void test_arena_spin_lock_size(int size) goto end_barrier; } + if (skel->data->test_skip == 3) { + printf("%s:SKIP: CONFIG_NR_CPUS exceed the maximum supported by arena spinlock\n", + __func__); + test__skip(); + goto end_barrier; + } + ASSERT_EQ(skel->bss->counter, repeat * nthreads, "check counter value"); end_barrier: diff --git a/tools/testing/selftests/bpf/progs/arena_spin_lock.c b/tools/testing/selftests/bpf/progs/arena_spin_lock.c index c4500c37f85e..086b57a426cf 100644 --- a/tools/testing/selftests/bpf/progs/arena_spin_lock.c +++ b/tools/testing/selftests/bpf/progs/arena_spin_lock.c @@ -37,8 +37,11 @@ int prog(void *ctx) #if defined(ENABLE_ATOMICS_TESTS) && defined(__BPF_FEATURE_ADDR_SPACE_CAST) unsigned long flags; - if ((ret = arena_spin_lock_irqsave(&lock, flags))) + if ((ret = arena_spin_lock_irqsave(&lock, flags))) { + if (ret == -EOPNOTSUPP) + test_skip = 3; return ret; + } if (counter != limit) counter++; bpf_repeat(cs_count); -- 2.43.5

3 months

2
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[PATCH RESEND v2] kunit: Enable PCI on UML without triggering WARN()

by Thomas Weißschuh

Various KUnit tests require PCI infrastructure to work. All normal platforms enable PCI by default, but UML does not. Enabling PCI from .kunitconfig files is problematic as it would not be portable. So in commit 6fc3a8636a7b ("kunit: tool: Enable virtio/PCI by default on UML") PCI was enabled by way of CONFIG_UML_PCI_OVER_VIRTIO=y. However CONFIG_UML_PCI_OVER_VIRTIO requires additional configuration of CONFIG_UML_PCI_OVER_VIRTIO_DEVICE_ID or will otherwise trigger a WARN() in virtio_pcidev_init(). However there is no one correct value for UML_PCI_OVER_VIRTIO_DEVICE_ID which could be used by default. This warning is confusing when debugging test failures. On the other hand, the functionality of CONFIG_UML_PCI_OVER_VIRTIO is not used at all, given that it is completely non-functional as indicated by the WARN() in question. Instead it is only used as a way to enable CONFIG_UML_PCI which itself is not directly configurable. Instead of going through CONFIG_UML_PCI_OVER_VIRTIO, introduce a custom configuration option which enables CONFIG_UML_PCI without triggering warnings or building dead code. Signed-off-by: Thomas Weißschuh <thomas.weissschuh(a)linutronix.de> Reviewed-by: Johannes Berg <johannes(a)sipsolutions.net> --- Changes in v2: - Rebase onto v6.17-rc1 - Pick up review from Johannes - Link to v1: https://lore.kernel.org/r/20250627-kunit-uml-pci-v1-1-a622fa445e58@linutron… --- lib/kunit/Kconfig | 7 +++++++ tools/testing/kunit/configs/arch_uml.config | 5 ++--- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/lib/kunit/Kconfig b/lib/kunit/Kconfig index c10ede4b1d2201d5f8cddeb71cc5096e21be9b6a..1823539e96da30e165fa8d395ccbd3f6754c836e 100644 --- a/lib/kunit/Kconfig +++ b/lib/kunit/Kconfig @@ -106,4 +106,11 @@ config KUNIT_DEFAULT_TIMEOUT If unsure, the default timeout of 300 seconds is suitable for most cases. +config KUNIT_UML_PCI + bool "KUnit UML PCI Support" + depends on UML + select UML_PCI + help + Enables the PCI subsystem on UML for use by KUnit tests. + endif # KUNIT diff --git a/tools/testing/kunit/configs/arch_uml.config b/tools/testing/kunit/configs/arch_uml.config index 54ad8972681a2cc724e6122b19407188910b9025..28edf816aa70e6f408d9486efff8898df79ee090 100644 --- a/tools/testing/kunit/configs/arch_uml.config +++ b/tools/testing/kunit/configs/arch_uml.config @@ -1,8 +1,7 @@ # Config options which are added to UML builds by default -# Enable virtio/pci, as a lot of tests require it. -CONFIG_VIRTIO_UML=y -CONFIG_UML_PCI_OVER_VIRTIO=y +# Enable pci, as a lot of tests require it. +CONFIG_KUNIT_UML_PCI=y # Enable FORTIFY_SOURCE for wider checking. CONFIG_FORTIFY_SOURCE=y --- base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585 change-id: 20250626-kunit-uml-pci-a2b687553746 Best regards, -- Thomas Weißschuh <thomas.weissschuh(a)linutronix.de>

3 months

4
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[PATCH 0/2] selftests/mm: Add -Wunreachable-code and fix warnings

by Muhammad Usama Anjum

This series is trimmed down version of previous more generic series[1]. In this new series, only -wunreachable-code flag is being added and dead code is being removed from generated warnings. [1] https://lore.kernel.org/all/20250822082145.4145617-1-usama.anjum@collabora.… Muhammad Usama Anjum (2): selftests/mm: Add -Wunreachable-code and fix warnings selftests/mm: protection_keys: Fix dead code tools/testing/selftests/mm/Makefile | 1 + tools/testing/selftests/mm/hmm-tests.c | 5 ++--- tools/testing/selftests/mm/pkey_sighandler_tests.c | 2 +- tools/testing/selftests/mm/protection_keys.c | 4 +--- tools/testing/selftests/mm/split_huge_page_test.c | 2 +- 5 files changed, 6 insertions(+), 8 deletions(-) -- 2.47.3

3 months

3
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[PATCH v20 0/8] fork: Support shadow stacks in clone3()

by Mark Brown

[ I think at this point everyone is OK with the ABI, and the x86 implementation has been tested so hopefully we are near to being able to get this merged? If there are any outstanding issues let me know and I can look at addressing them. The one possible issue I am aware of is that the RISC-V shadow stack support was briefly in -next but got dropped along with the general RISC-V issues during the last merge window, rebasing for that is still in progress. I guess ideally this could be applied on a branch and then pulled into the RISC-V tree? ] The kernel has recently added support for shadow stacks, currently x86 only using their CET feature but both arm64 and RISC-V have equivalent features (GCS and Zicfiss respectively), I am actively working on GCS[1]. With shadow stacks the hardware maintains an additional stack containing only the return addresses for branch instructions which is not generally writeable by userspace and ensures that any returns are to the recorded addresses. This provides some protection against ROP attacks and making it easier to collect call stacks. These shadow stacks are allocated in the address space of the userspace process. Our API for shadow stacks does not currently offer userspace any flexiblity for managing the allocation of shadow stacks for newly created threads, instead the kernel allocates a new shadow stack with the same size as the normal stack whenever a thread is created with the feature enabled. The stacks allocated in this way are freed by the kernel when the thread exits or shadow stacks are disabled for the thread. This lack of flexibility and control isn't ideal, in the vast majority of cases the shadow stack will be over allocated and the implicit allocation and deallocation is not consistent with other interfaces. As far as I can tell the interface is done in this manner mainly because the shadow stack patches were in development since before clone3() was implemented. Since clone3() is readily extensible let's add support for specifying a shadow stack when creating a new thread or process, keeping the current implicit allocation behaviour if one is not specified either with clone3() or through the use of clone(). The user must provide a shadow stack pointer, this must point to memory mapped for use as a shadow stackby map_shadow_stack() with an architecture specified shadow stack token at the top of the stack. Yuri Khrustalev has raised questions from the libc side regarding discoverability of extended clone3() structure sizes[2], this seems like a general issue with clone3(). There was a suggestion to add a hwcap on arm64 which isn't ideal but is doable there, though architecture specific mechanisms would also be needed for x86 (and RISC-V if it's support gets merged before this does). The idea has, however, had strong pushback from the architecture maintainers and it is possible to detect support for this in clone3() by attempting a call with a misaligned shadow stack pointer specified so no hwcap has been added. [1] https://lore.kernel.org/linux-arm-kernel/20241001-arm64-gcs-v13-0-222b78d87… [2] https://lore.kernel.org/r/aCs65ccRQtJBnZ_5@arm.com Signed-off-by: Mark Brown <broonie(a)kernel.org> --- Changes in v20: - Comment fixes and clarifications in x86 arch_shstk_validate_clone() from Rick Edgecombe. - Spelling fix in documentation. - Link to v19: https://lore.kernel.org/r/20250819-clone3-shadow-stack-v19-0-bc957075479b@k… Changes in v19: - Rebase onto v6.17-rc1. - Link to v18: https://lore.kernel.org/r/20250702-clone3-shadow-stack-v18-0-7965d2b694db@k… Changes in v18: - Rebase onto v6.16-rc3. - Thanks to pointers from Yuri Khrustalev this version has been tested on x86 so I have removed the RFT tag. - Clarify clone3_shadow_stack_valid() comment about the Kconfig check. - Remove redundant GCSB DSYNCs in arm64 code. - Fix token validation on x86. - Link to v17: https://lore.kernel.org/r/20250609-clone3-shadow-stack-v17-0-8840ed97ff6f@k… Changes in v17: - Rebase onto v6.16-rc1. - Link to v16: https://lore.kernel.org/r/20250416-clone3-shadow-stack-v16-0-2ffc9ca3917b@k… Changes in v16: - Rebase onto v6.15-rc2. - Roll in fixes from x86 testing from Rick Edgecombe. - Rework so that the argument is shadow_stack_token. - Link to v15: https://lore.kernel.org/r/20250408-clone3-shadow-stack-v15-0-3fa245c6e3be@k… Changes in v15: - Rebase onto v6.15-rc1. - Link to v14: https://lore.kernel.org/r/20250206-clone3-shadow-stack-v14-0-805b53af73b9@k… Changes in v14: - Rebase onto v6.14-rc1. - Link to v13: https://lore.kernel.org/r/20241203-clone3-shadow-stack-v13-0-93b89a81a5ed@k… Changes in v13: - Rebase onto v6.13-rc1. - Link to v12: https://lore.kernel.org/r/20241031-clone3-shadow-stack-v12-0-7183eb8bee17@k… Changes in v12: - Add the regular prctl() to the userspace API document since arm64 support is queued in -next. - Link to v11: https://lore.kernel.org/r/20241005-clone3-shadow-stack-v11-0-2a6a2bd6d651@k… Changes in v11: - Rebase onto arm64 for-next/gcs, which is based on v6.12-rc1, and integrate arm64 support. - Rework the interface to specify a shadow stack pointer rather than a base and size like we do for the regular stack. - Link to v10: https://lore.kernel.org/r/20240821-clone3-shadow-stack-v10-0-06e8797b9445@k… Changes in v10: - Integrate fixes & improvements for the x86 implementation from Rick Edgecombe. - Require that the shadow stack be VM_WRITE. - Require that the shadow stack base and size be sizeof(void *) aligned. - Clean up trailing newline. - Link to v9: https://lore.kernel.org/r/20240819-clone3-shadow-stack-v9-0-962d74f99464@ke… Changes in v9: - Pull token validation earlier and report problems with an error return to parent rather than signal delivery to the child. - Verify that the top of the supplied shadow stack is VM_SHADOW_STACK. - Rework token validation to only do the page mapping once. - Drop no longer needed support for testing for signals in selftest. - Fix typo in comments. - Link to v8: https://lore.kernel.org/r/20240808-clone3-shadow-stack-v8-0-0acf37caf14c@ke… Changes in v8: - Fix token verification with user specified shadow stack. - Don't track user managed shadow stacks for child processes. - Link to v7: https://lore.kernel.org/r/20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@ke… Changes in v7: - Rebase onto v6.11-rc1. - Typo fixes. - Link to v6: https://lore.kernel.org/r/20240623-clone3-shadow-stack-v6-0-9ee7783b1fb9@ke… Changes in v6: - Rebase onto v6.10-rc3. - Ensure we don't try to free the parent shadow stack in error paths of x86 arch code. - Spelling fixes in userspace API document. - Additional cleanups and improvements to the clone3() tests to support the shadow stack tests. - Link to v5: https://lore.kernel.org/r/20240203-clone3-shadow-stack-v5-0-322c69598e4b@ke… Changes in v5: - Rebase onto v6.8-rc2. - Rework ABI to have the user allocate the shadow stack memory with map_shadow_stack() and a token. - Force inlining of the x86 shadow stack enablement. - Move shadow stack enablement out into a shared header for reuse by other tests. - Link to v4: https://lore.kernel.org/r/20231128-clone3-shadow-stack-v4-0-8b28ffe4f676@ke… Changes in v4: - Formatting changes. - Use a define for minimum shadow stack size and move some basic validation to fork.c. - Link to v3: https://lore.kernel.org/r/20231120-clone3-shadow-stack-v3-0-a7b8ed3e2acc@ke… Changes in v3: - Rebase onto v6.7-rc2. - Remove stale shadow_stack in internal kargs. - If a shadow stack is specified unconditionally use it regardless of CLONE_ parameters. - Force enable shadow stacks in the selftest. - Update changelogs for RISC-V feature rename. - Link to v2: https://lore.kernel.org/r/20231114-clone3-shadow-stack-v2-0-b613f8681155@ke… Changes in v2: - Rebase onto v6.7-rc1. - Remove ability to provide preallocated shadow stack, just specify the desired size. - Link to v1: https://lore.kernel.org/r/20231023-clone3-shadow-stack-v1-0-d867d0b5d4d0@ke… --- Mark Brown (8): arm64/gcs: Return a success value from gcs_alloc_thread_stack() Documentation: userspace-api: Add shadow stack API documentation selftests: Provide helper header for shadow stack testing fork: Add shadow stack support to clone3() selftests/clone3: Remove redundant flushes of output streams selftests/clone3: Factor more of main loop into test_clone3() selftests/clone3: Allow tests to flag if -E2BIG is a valid error code selftests/clone3: Test shadow stack support Documentation/userspace-api/index.rst | 1 + Documentation/userspace-api/shadow_stack.rst | 44 +++++ arch/arm64/include/asm/gcs.h | 8 +- arch/arm64/kernel/process.c | 8 +- arch/arm64/mm/gcs.c | 55 +++++- arch/x86/include/asm/shstk.h | 11 +- arch/x86/kernel/process.c | 2 +- arch/x86/kernel/shstk.c | 53 ++++- include/asm-generic/cacheflush.h | 11 ++ include/linux/sched/task.h | 17 ++ include/uapi/linux/sched.h | 9 +- kernel/fork.c | 93 +++++++-- tools/testing/selftests/clone3/clone3.c | 226 ++++++++++++++++++---- tools/testing/selftests/clone3/clone3_selftests.h | 65 ++++++- tools/testing/selftests/ksft_shstk.h | 98 ++++++++++ 15 files changed, 620 insertions(+), 81 deletions(-) --- base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585 change-id: 20231019-clone3-shadow-stack-15d40d2bf536 Best regards, -- Mark Brown <broonie(a)kernel.org>

3 months

5
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[PATCH v4 0/4] procfs: make reference pidns more user-visible

by Aleksa Sarai

Ever since the introduction of pid namespaces, procfs has had very implicit behaviour surrounding them (the pidns used by a procfs mount is auto-selected based on the mounting process's active pidns, and the pidns itself is basically hidden once the mount has been constructed). /* pidns mount option for procfs */ This implicit behaviour has historically meant that userspace was required to do some special dances in order to configure the pidns of a procfs mount as desired. Examples include: * In order to bypass the mnt_too_revealing() check, Kubernetes creates a procfs mount from an empty pidns so that user namespaced containers can be nested (without this, the nested containers would fail to mount procfs). But this requires forking off a helper process because you cannot just one-shot this using mount(2). * Container runtimes in general need to fork into a container before configuring its mounts, which can lead to security issues in the case of shared-pidns containers (a privileged process in the pidns can interact with your container runtime process). While SUID_DUMP_DISABLE and user namespaces make this less of an issue, the strict need for this due to a minor uAPI wart is kind of unfortunate. Things would be much easier if there was a way for userspace to just specify the pidns they want. Patch 1 implements a new "pidns" argument which can be set using fsconfig(2): fsconfig(procfd, FSCONFIG_SET_FD, "pidns", NULL, nsfd); fsconfig(procfd, FSCONFIG_SET_STRING, "pidns", "/proc/self/ns/pid", 0); or classic mount(2) / mount(8): // mount -t proc -o pidns=/proc/self/ns/pid proc /tmp/proc mount("proc", "/tmp/proc", "proc", MS_..., "pidns=/proc/self/ns/pid"); The initial security model I have in this RFC is to be as conservative as possible and just mirror the security model for setns(2) -- which means that you can only set pidns=... to pid namespaces that your current pid namespace is a direct ancestor of and you have CAP_SYS_ADMIN privileges over the pid namespace. This fulfils the requirements of container runtimes, but I suspect that this may be too strict for some usecases. The pidns argument is not displayed in mountinfo -- it's not clear to me what value it would make sense to show (maybe we could just use ns_dname to provide an identifier for the namespace, but this number would be fairly useless to userspace). I'm open to suggestions. Note that PROCFS_GET_PID_NAMESPACE (see below) does at least let userspace get information about this outside of mountinfo. Note that you cannot change the pidns of an already-created procfs instance. The primary reason is that allowing this to be changed would require RCU-protecting proc_pid_ns(sb) and thus auditing all of fs/proc/* and some of the users in fs/* to make sure they wouldn't UAF the pid namespace. Since creating procfs instances is very cheap, it seems unnecessary to overcomplicate this upfront. Trying to reconfigure procfs this way errors out with -EBUSY. /* ioctl(PROCFS_GET_PID_NAMESPACE) */ In addition, being able to figure out what pid namespace is being used by a procfs mount is quite useful when you have an administrative process (such as a container runtime) which wants to figure out the correct way of mapping PIDs between its own namespace and the namespace for procfs (using NS_GET_{PID,TGID}_{IN,FROM}_PIDNS). There are alternative ways to do this, but they all rely on ancillary information that third-party libraries and tools do not necessarily have access to. To make this easier, add a new ioctl (PROCFS_GET_PID_NAMESPACE) which can be used to get a reference to the pidns that a procfs is using. Rather than copying the (fairly strict) security model for setns(2), apply a slightly looser model to better match what userspace can already do: * Make the ioctl only valid on the root (meaning that a process without access to the procfs root -- such as only having an fd to a procfs file or some open_tree(2)-like subset -- cannot use this API). This means that the process already has some level of access to the /proc/$pid directories. * If the calling process is in an ancestor pidns, then they can already create pidfd for processes inside the pidns, which is morally equivalent to a pidns file descriptor according to setns(2). So it seems reasonable to just allow it in this case. (The justification for this model was suggested by Christian.) * If the process has access to /proc/1/ns/pid already (i.e. has ptrace-read access to the pidns pid1), then this ioctl is equivalent to just opening a handle to it that way. Ideally we would check for ptrace-read access against all processes in the pidns (which is very likely to be true for at least one process, as SUID_DUMP_DISABLE is cleared on exec(2) and is rarely set by most programs), but this would obviously not scale. I'm open to suggestions for whether we need to make this stricter (or possibly allow more cases). Signed-off-by: Aleksa Sarai <cyphar(a)cyphar.com> --- Changes in v4: - Remove unneeded EXPORT_SYMBOL_GPL. [Christian Brauner] - Return -EOPNOTSUPP for new APIs for CONFIG_PID_NS=n rather than pretending they don't exist entirely. [Christian Brauner] - PROCFS_IOCTL_MAGIC conflicts with XSDFEC_MAGIC, so we need to allocate subvalues more carefully (switch to _IO(PROCFS_IOCTL_MAGIC, 32)). - Add some more selftests for PROCFS_GET_PID_NAMESPACE. - Reword argument for PROCFS_GET_PID_NAMESPACE security model based on Christian's suggestion, and remove CAP_SYS_ADMIN edge-case (in most cases, such a process would also have ptrace-read credentials over the pidns pid1). - v3: <https://lore.kernel.org/r/20250724-procfs-pidns-api-v3-0-4c685c910923@cypha…> Changes in v3: - Disallow changing pidns for existing procfs instances, as we'd probably have to RCU-protect everything that touches the pinned pidns reference. - Improve tests with slightly nicer ASSERT_ERRNO* macros. - v2: <https://lore.kernel.org/r/20250723-procfs-pidns-api-v2-0-621e7edd8e40@cypha…> Changes in v2: - #ifdef CONFIG_PID_NS - Improve cover letter wording to make it clear we're talking about two separate features with different permission models. [Andy Lutomirski] - Fix build warnings in pidns_is_ancestor() patch. [kernel test robot] - v1: <https://lore.kernel.org/r/20250721-procfs-pidns-api-v1-0-5cd9007e512d@cypha…> --- Aleksa Sarai (4): pidns: move is-ancestor logic to helper procfs: add "pidns" mount option procfs: add PROCFS_GET_PID_NAMESPACE ioctl selftests/proc: add tests for new pidns APIs Documentation/filesystems/proc.rst | 12 ++ fs/proc/root.c | 166 +++++++++++++++- include/linux/pid_namespace.h | 9 + include/uapi/linux/fs.h | 4 + kernel/pid_namespace.c | 22 ++- tools/testing/selftests/proc/.gitignore | 1 + tools/testing/selftests/proc/Makefile | 1 + tools/testing/selftests/proc/proc-pidns.c | 315 ++++++++++++++++++++++++++++++ 8 files changed, 514 insertions(+), 16 deletions(-) --- base-commit: 66639db858112bf6b0f76677f7517643d586e575 change-id: 20250717-procfs-pidns-api-8ed1583431f0 Best regards, -- Aleksa Sarai <cyphar(a)cyphar.com>

3 months

4
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[PATCH 0/9] Start porting UML to nolibc

by Benjamin Berg

From: Benjamin Berg <benjamin.berg(a)intel.com> For a while now, we have discussed that it may be better to avoid using libc inside UML as it may be interfering in unexpected ways with kernel functionality. A major point of concern is that there is no guarantee that the libc is not using any address space that may conflict with kernel addresses. This patchset is an attempt to start a nolibc port of UML. The goal is to port UML to use nolibc in smaller chunks to make the switch more manageable. There are three parts to this patchset: * Two patches to use tools/include headers instead of kernel headers for userspace files. * A few nolibc fixes and a new NOLIBC_NO_STARTCODE compile flag for it * Finally nolibc build support for UML and switching two files The first two parts could be merged independently. The last step to use nolibc inside UML obviously depends on the first two. Benjamin Benjamin Berg (9): tools compiler.h: fix __used definition um: use tools/include for user files tools/nolibc/stdio: remove perror if NOLIBC_IGNORE_ERRNO is set tools/nolibc/dirent: avoid errno in readdir_r tools/nolibc: use __fallthrough__ rather than fallthrough tools/nolibc: add option to disable startup code um: add infrastructure to build files using nolibc um: use nolibc for the --showconfig implementation um: switch ptrace FP register access to nolibc arch/um/Makefile | 32 ++++++++++++++++--- .../um/include/shared/generated/asm-offsets.h | 1 + .../include/shared/generated/user_constants.h | 1 + arch/um/include/shared/init.h | 2 +- arch/um/include/shared/os.h | 2 ++ arch/um/include/shared/user.h | 5 --- arch/um/kernel/Makefile | 2 +- arch/um/kernel/skas/stub.c | 1 + arch/um/kernel/skas/stub_exe.c | 4 +-- arch/um/os-Linux/skas/process.c | 6 ++-- arch/um/os-Linux/start_up.c | 4 +-- arch/um/scripts/Makefile.rules | 10 ++++-- arch/x86/um/Makefile | 6 ++-- arch/x86/um/os-Linux/Makefile | 5 ++- arch/x86/um/os-Linux/registers.c | 22 +++++-------- arch/x86/um/user-offsets.c | 1 - tools/include/linux/compiler.h | 2 +- tools/include/nolibc/arch-arm.h | 2 ++ tools/include/nolibc/arch-arm64.h | 2 ++ tools/include/nolibc/arch-loongarch.h | 2 ++ tools/include/nolibc/arch-m68k.h | 2 ++ tools/include/nolibc/arch-mips.h | 2 ++ tools/include/nolibc/arch-powerpc.h | 2 ++ tools/include/nolibc/arch-riscv.h | 2 ++ tools/include/nolibc/arch-s390.h | 2 ++ tools/include/nolibc/arch-sh.h | 2 ++ tools/include/nolibc/arch-sparc.h | 2 ++ tools/include/nolibc/arch-x86.h | 4 +++ tools/include/nolibc/compiler.h | 4 +-- tools/include/nolibc/crt.h | 3 ++ tools/include/nolibc/dirent.h | 6 ++-- tools/include/nolibc/stackprotector.h | 2 ++ tools/include/nolibc/stdio.h | 2 ++ tools/include/nolibc/stdlib.h | 2 ++ tools/include/nolibc/sys.h | 3 +- tools/include/nolibc/sys/auxv.h | 3 ++ 36 files changed, 108 insertions(+), 47 deletions(-) create mode 120000 arch/um/include/shared/generated/asm-offsets.h create mode 120000 arch/um/include/shared/generated/user_constants.h -- 2.51.0

3 months

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Re: [PATCH v4 3/3] fs/proc/task_mmu: execute PROCMAP_QUERY ioctl under per-vma locks

by Suren Baghdasaryan

On Sun, Sep 14, 2025 at 6:24 AM Chris Mason <clm(a)meta.com> wrote: > > On Fri, 8 Aug 2025 08:28:49 -0700 Suren Baghdasaryan <surenb(a)google.com> wrote: > > > Utilize per-vma locks to stabilize vma after lookup without taking > > mmap_lock during PROCMAP_QUERY ioctl execution. If vma lock is > > contended, we fall back to mmap_lock but take it only momentarily > > to lock the vma and release the mmap_lock. In a very unlikely case > > of vm_refcnt overflow, this fall back path will fail and ioctl is > > done under mmap_lock protection. > > > > This change is designed to reduce mmap_lock contention and prevent > > PROCMAP_QUERY ioctl calls from blocking address space updates. > > > > Signed-off-by: Suren Baghdasaryan <surenb(a)google.com> > > Acked-by: SeongJae Park <sj(a)kernel.org> > > --- > > fs/proc/task_mmu.c | 103 +++++++++++++++++++++++++++++++++++++-------- > > 1 file changed, 85 insertions(+), 18 deletions(-) > > > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > > index c0968d293b61..e64cf40ce9c4 100644 > > --- a/fs/proc/task_mmu.c > > +++ b/fs/proc/task_mmu.c > > @@ -132,6 +132,12 @@ static void release_task_mempolicy(struct proc_maps_private *priv) > > [ ... ] > > > +static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_locking_ctx *lock_ctx, > > + unsigned long addr) > > +{ > > + struct mm_struct *mm = lock_ctx->mm; > > + struct vm_area_struct *vma; > > + struct vma_iterator vmi; > > + > > + if (lock_ctx->mmap_locked) > > + return find_vma(mm, addr); > > + > > + /* Unlock previously locked VMA and find the next one under RCU */ > > + unlock_ctx_vma(lock_ctx); > > + rcu_read_lock(); > > + vma_iter_init(&vmi, mm, addr); > > + vma = lock_next_vma(mm, &vmi, addr); > > + rcu_read_unlock(); > > + > > + if (!vma) > > + return NULL; > > + > > + if (!IS_ERR(vma)) { > > + lock_ctx->locked_vma = vma; > > + return vma; > > + } > > + > > + if (PTR_ERR(vma) == -EAGAIN) { > > + /* Fallback to mmap_lock on vma->vm_refcnt overflow */ > > + mmap_read_lock(mm); > > I know it's just a (very rare) fallback, but should we be using > mmap_read_lock_killable() for consistency? I can see this impacting oom > kills or other times we really want to be able to get rid of procs. That's a good idea. From a quick look it seems safe to fail with -EINTR here, which will propagate all the way to do_procmap_query(). Do you want to post a fixup patch? Thanks, Suren. > > -chris

3 months

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Re: [syzbot] [net?] WARNING: suspicious RCU usage in corrupted (3)

by syzbot

syzbot suspects this issue was fixed by commit: commit 7f12c33850482521c961c5c15a50ebe9b9a88d1e Author: Charalampos Mitrodimas <charmitro(a)posteo.net> Date: Wed Jun 11 17:20:43 2025 +0000 net, bpf: Fix RCU usage in task_cls_state() for BPF programs bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13745562580000 start commit: 079e5c56a5c4 bpf: Fix error return value in bpf_copy_from_.. git tree: bpf-next kernel config: https://syzkaller.appspot.com/x/.config?x=c6c517d2f439239 dashboard link: https://syzkaller.appspot.com/bug?extid=9767c7ed68b95cfa69e6 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=114915f4580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15566170580000 If the result looks correct, please mark the issue as fixed by replying with: #syz fix: net, bpf: Fix RCU usage in task_cls_state() for BPF programs For information about bisection process see: https://goo.gl/tpsmEJ#bisection

3 months

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[PATCH net v2 0/2] net: dst_metadata: fix DF flag extraction on tunnel rx

by Ilya Maximets

Two patches here, first fixes the issue where tunnel core doesn't actually extract DF bit from the outer IP header, even though both OVS and TC flower allow matching on it. More details in the commit message. The second is a selftest for openvswitch that reproduces the issue, but also just adds some basic coverage for the tunnel metadata extraction and related openvswitch uAPI. Version 2: * Added missing tun_dst NULL check. * Added Reviewed-by from Aaron for the selftest. Version 1: https://lore.kernel.org/netdev/20250905133105.3940420-1-i.maximets@ovn.org/ Ilya Maximets (2): net: dst_metadata: fix IP_DF bit not extracted from tunnel headers selftests: openvswitch: add a simple test for tunnel metadata include/net/dst_metadata.h | 11 ++- .../selftests/net/openvswitch/openvswitch.sh | 88 +++++++++++++++++-- 2 files changed, 90 insertions(+), 9 deletions(-) -- 2.50.1

3 months

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[PATCH v16 0/6] KVM: arm64: Provide guest support for GCS

by Mark Brown

The arm64 Guarded Control Stack (GCS) feature provides support for hardware protected stacks of return addresses, intended to provide hardening against return oriented programming (ROP) attacks and to make it easier to gather call stacks for applications such as profiling. When GCS is active a secondary stack called the Guarded Control Stack is maintained, protected with a memory attribute which means that it can only be written with specific GCS operations. The current GCS pointer can not be directly written to by userspace. When a BL is executed the value stored in LR is also pushed onto the GCS, and when a RET is executed the top of the GCS is popped and compared to LR with a fault being raised if the values do not match. GCS operations may only be performed on GCS pages, a data abort is generated if they are not. The combination of hardware enforcement and lack of extra instructions in the function entry and exit paths should result in something which has less overhead and is more difficult to attack than a purely software implementation like clang's shadow stacks. This series implements support for managing GCS for KVM guests. Signed-off-by: Mark Brown <broonie(a)kernel.org> --- Changes in v16: - Rebase onto v6.17-rc3. - Also expose the feature to nested guests. - Implement emulation of EXLOCK when returning from nested guests. - Rename enter_exception_gcs() to compute_exlock(). - Move all ID_AA64PFR1_EL1 handling to the final kernel patch. - Drop unneeded forwarding of GCS exceptions. - Commit and cover message updates. - Link to v15: https://lore.kernel.org/r/20250820-arm64-gcs-v15-0-5e334da18b84@kernel.org Changes in v15: - Rebase onto v6.17-rc1. - Link to v14: https://lore.kernel.org/r/20241005-arm64-gcs-v14-0-59060cd6092b@kernel.org Changes in v14: - Rebase onto arm64/for-next/gcs which includes all the non-KVM support. - Manage the fine grained traps for GCS instructions. - Manage PSTATE.EXLOCK when delivering exceptions to KVM guests. - Link to v13: https://lore.kernel.org/r/20241001-arm64-gcs-v13-0-222b78d87eee@kernel.org Changes in v13: - Rebase onto v6.12-rc1. - Allocate VM_HIGH_ARCH_6 since protection keys used all the existing bits. - Implement mm_release() and free transparently allocated GCSs there. - Use bit 32 of AT_HWCAP for GCS due to AT_HWCAP2 being filled. - Since we now only set GCSCRE0_EL1 on change ensure that it is initialised with GCSPR_EL0 accessible to EL0. - Fix OOM handling on thread copy. - Link to v12: https://lore.kernel.org/r/20240829-arm64-gcs-v12-0-42fec947436a@kernel.org Changes in v12: - Clarify and simplify the signal handling code so we work with the register state. - When checking for write aborts to shadow stack pages ensure the fault is a data abort. - Depend on !UPROBES. - Comment cleanups. - Link to v11: https://lore.kernel.org/r/20240822-arm64-gcs-v11-0-41b81947ecb5@kernel.org Changes in v11: - Remove the dependency on the addition of clone3() support for shadow stacks, rebasing onto v6.11-rc3. - Make ID_AA64PFR1_EL1.GCS writeable in KVM. - Hide GCS registers when GCS is not enabled for KVM guests. - Require HCRX_EL2.GCSEn if booting at EL1. - Require that GCSCR_EL1 and GCSCRE0_EL1 be initialised regardless of if we boot at EL2 or EL1. - Remove some stray use of bit 63 in signal cap tokens. - Warn if we see a GCS with VM_SHARED. - Remove rdundant check for VM_WRITE in fault handling. - Cleanups and clarifications in the ABI document. - Clean up and improve documentation of some sync placement. - Only set the EL0 GCS mode if it's actually changed. - Various minor fixes and tweaks. - Link to v10: https://lore.kernel.org/r/20240801-arm64-gcs-v10-0-699e2bd2190b@kernel.org Changes in v10: - Fix issues with THP. - Tighten up requirements for initialising GCSCR*. - Only generate GCS signal frames for threads using GCS. - Only context switch EL1 GCS registers if S1PIE is enabled. - Move context switch of GCSCRE0_EL1 to EL0 context switch. - Make GCS registers unconditionally visible to userspace. - Use FHU infrastructure. - Don't change writability of ID_AA64PFR1_EL1 for KVM. - Remove unused arguments from alloc_gcs(). - Typo fixes. - Link to v9: https://lore.kernel.org/r/20240625-arm64-gcs-v9-0-0f634469b8f0@kernel.org Changes in v9: - Rebase onto v6.10-rc3. - Restructure and clarify memory management fault handling. - Fix up basic-gcs for the latest clone3() changes. - Convert to newly merged KVM ID register based feature configuration. - Fixes for NV traps. - Link to v8: https://lore.kernel.org/r/20240203-arm64-gcs-v8-0-c9fec77673ef@kernel.org Changes in v8: - Invalidate signal cap token on stack when consuming. - Typo and other trivial fixes. - Don't try to use process_vm_write() on GCS, it intentionally does not work. - Fix leak of thread GCSs. - Rebase onto latest clone3() series. - Link to v7: https://lore.kernel.org/r/20231122-arm64-gcs-v7-0-201c483bd775@kernel.org Changes in v7: - Rebase onto v6.7-rc2 via the clone3() patch series. - Change the token used to cap the stack during signal handling to be compatible with GCSPOPM. - Fix flags for new page types. - Fold in support for clone3(). - Replace copy_to_user_gcs() with put_user_gcs(). - Link to v6: https://lore.kernel.org/r/20231009-arm64-gcs-v6-0-78e55deaa4dd@kernel.org Changes in v6: - Rebase onto v6.6-rc3. - Add some more gcsb_dsync() barriers following spec clarifications. - Due to ongoing discussion around clone()/clone3() I've not updated anything there, the behaviour is the same as on previous versions. - Link to v5: https://lore.kernel.org/r/20230822-arm64-gcs-v5-0-9ef181dd6324@kernel.org Changes in v5: - Don't map any permissions for user GCSs, we always use EL0 accessors or use a separate mapping of the page. - Reduce the standard size of the GCS to RLIMIT_STACK/2. - Enforce a PAGE_SIZE alignment requirement on map_shadow_stack(). - Clarifications and fixes to documentation. - More tests. - Link to v4: https://lore.kernel.org/r/20230807-arm64-gcs-v4-0-68cfa37f9069@kernel.org Changes in v4: - Implement flags for map_shadow_stack() allowing the cap and end of stack marker to be enabled independently or not at all. - Relax size and alignment requirements for map_shadow_stack(). - Add more blurb explaining the advantages of hardware enforcement. - Link to v3: https://lore.kernel.org/r/20230731-arm64-gcs-v3-0-cddf9f980d98@kernel.org Changes in v3: - Rebase onto v6.5-rc4. - Add a GCS barrier on context switch. - Add a GCS stress test. - Link to v2: https://lore.kernel.org/r/20230724-arm64-gcs-v2-0-dc2c1d44c2eb@kernel.org Changes in v2: - Rebase onto v6.5-rc3. - Rework prctl() interface to allow each bit to be locked independently. - map_shadow_stack() now places the cap token based on the size requested by the caller not the actual space allocated. - Mode changes other than enable via ptrace are now supported. - Expand test coverage. - Various smaller fixes and adjustments. - Link to v1: https://lore.kernel.org/r/20230716-arm64-gcs-v1-0-bf567f93bba6@kernel.org --- Mark Brown (6): arm64/gcs: Ensure FGTs for EL1 GCS instructions are disabled KVM: arm64: Manage GCS access and registers for guests KVM: arm64: Set PSTATE.EXLOCK when entering an exception KVM: arm64: Validate GCS exception lock when emulating ERET KVM: arm64: Allow GCS to be enabled for guests KVM: selftests: arm64: Add GCS registers to get-reg-list arch/arm64/include/asm/el2_setup.h | 5 +++ arch/arm64/include/asm/kvm_emulate.h | 3 ++ arch/arm64/include/asm/kvm_host.h | 14 +++++++++ arch/arm64/include/asm/vncr_mapping.h | 2 ++ arch/arm64/include/uapi/asm/ptrace.h | 1 + arch/arm64/kvm/emulate-nested.c | 40 +++++++++++++++++++++++- arch/arm64/kvm/hyp/exception.c | 37 ++++++++++++++++++++++ arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 31 ++++++++++++++++++ arch/arm64/kvm/hyp/vhe/sysreg-sr.c | 10 ++++++ arch/arm64/kvm/nested.c | 7 +++-- arch/arm64/kvm/sys_regs.c | 32 +++++++++++++++++-- tools/testing/selftests/kvm/arm64/get-reg-list.c | 12 +++++++ 12 files changed, 188 insertions(+), 6 deletions(-) --- base-commit: 1b237f190eb3d36f52dffe07a40b5eb210280e00 change-id: 20230303-arm64-gcs-e311ab0d8729 Best regards, -- Mark Brown <broonie(a)kernel.org>

3 months, 1 week

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