user/sven/linux.git/kernel/fork.c, branch v6.12.4

Revert "fs: don't block i_writecount during exec"

2024-12-05T13:02:50Z

commit 3b832035387ff508fdcf0fba66701afc78f79e3d upstream. This reverts commit 2a010c41285345da60cece35575b4e0af7e7bf44. Rui Ueyama writes: > I'm the creator and the maintainer of the mold linker > (https://github.com/rui314/mold). Recently, we discovered that mold > started causing process crashes in certain situations due to a change > in the Linux kernel. Here are the details: > > - In general, overwriting an existing file is much faster than > creating an empty file and writing to it on Linux, so mold attempts to > reuse an existing executable file if it exists. > > - If a program is running, opening the executable file for writing > previously failed with ETXTBSY. If that happens, mold falls back to > creating a new file. > > - However, the Linux kernel recently changed the behavior so that > writing to an executable file is now always permitted > (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2a010c412853). > > That caused mold to write to an executable file even if there's a > process running that file. Since changes to mmap'ed files are > immediately visible to other processes, any processes running that > file would almost certainly crash in a very mysterious way. > Identifying the cause of these random crashes took us a few days. > > Rejecting writes to an executable file that is currently running is a > well-known behavior, and Linux had operated that way for a very long > time. So, I don’t believe relying on this behavior was our mistake; > rather, I see this as a regression in the Linux kernel. Quoting myself from commit 2a010c412853 ("fs: don't block i_writecount during exec") > Yes, someone in userspace could potentially be relying on this. It's not > completely out of the realm of possibility but let's find out if that's > actually the case and not guess. It seems we found out that someone is relying on this obscure behavior. So revert the change. Link: https://github.com/rui314/mold/issues/1361 Link: https://lore.kernel.org/r/4a2bc207-76be-4715-8e12-7fc45a76a125@leemhuis.info Cc: Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman

Merge tag 'timers-urgent-2024-11-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2024-11-03T18:22:21Z

Pull timer fix from Thomas Gleixner: "A single fix for posix CPU timers. When a thread is cloned, the posix CPU timers are not inherited. If the parent has a CPU timer armed the corresponding tick dependency in the tasks tick_dep_mask is set and copied to the new thread, which means the new thread and all decendants will prevent the system to go into full NOHZ operation. Clear the tick dependency mask in copy_process() to fix this" * tag 'timers-urgent-2024-11-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: posix-cpu-timers: Clear TICK_DEP_BIT_POSIX_TIMER on clone

fork: only invoke khugepaged, ksm hooks if no error

2024-10-29T04:40:39Z

There is no reason to invoke these hooks early against an mm that is in an incomplete state. The change in commit d24062914837 ("fork: use __mt_dup() to duplicate maple tree in dup_mmap()") makes this more pertinent as we may be in a state where entries in the maple tree are not yet consistent. Their placement early in dup_mmap() only appears to have been meaningful for early error checking, and since functionally it'd require a very small allocation to fail (in practice 'too small to fail') that'd only occur in the most dire circumstances, meaning the fork would fail or be OOM'd in any case. Since both khugepaged and KSM tracking are there to provide optimisations to memory performance rather than critical functionality, it doesn't really matter all that much if, under such dire memory pressure, we fail to register an mm with these. As a result, we follow the example of commit d2081b2bf819 ("mm: khugepaged: make khugepaged_enter() void function") and make ksm_fork() a void function also. We only expose the mm to these functions once we are done with them and only if no error occurred in the fork operation. Link: https://lkml.kernel.org/r/e0cb8b840c9d1d5a6e84d4f8eff5f3f2022aa10c.1729014377.git.lorenzo.stoakes@oracle.com Fixes: d24062914837 ("fork: use __mt_dup() to duplicate maple tree in dup_mmap()") Signed-off-by: Lorenzo Stoakes Reported-by: Jann Horn Reviewed-by: Liam R. Howlett Reviewed-by: Vlastimil Babka Reviewed-by: Jann Horn Cc: Alexander Viro Cc: Christian Brauner Cc: Jan Kara Cc: Linus Torvalds Cc: Signed-off-by: Andrew Morton

fork: do not invoke uffd on fork if error occurs

2024-10-29T04:40:38Z

Patch series "fork: do not expose incomplete mm on fork". During fork we may place the virtual memory address space into an inconsistent state before the fork operation is complete. In addition, we may encounter an error during the fork operation that indicates that the virtual memory address space is invalidated. As a result, we should not be exposing it in any way to external machinery that might interact with the mm or VMAs, machinery that is not designed to deal with incomplete state. We specifically update the fork logic to defer khugepaged and ksm to the end of the operation and only to be invoked if no error arose, and disallow uffd from observing fork events should an error have occurred. This patch (of 2): Currently on fork we expose the virtual address space of a process to userland unconditionally if uffd is registered in VMAs, regardless of whether an error arose in the fork. This is performed in dup_userfaultfd_complete() which is invoked unconditionally, and performs two duties - invoking registered handlers for the UFFD_EVENT_FORK event via dup_fctx(), and clearing down userfaultfd_fork_ctx objects established in dup_userfaultfd(). This is problematic, because the virtual address space may not yet be correctly initialised if an error arose. The change in commit d24062914837 ("fork: use __mt_dup() to duplicate maple tree in dup_mmap()") makes this more pertinent as we may be in a state where entries in the maple tree are not yet consistent. We address this by, on fork error, ensuring that we roll back state that we would otherwise expect to clean up through the event being handled by userland and perform the memory freeing duty otherwise performed by dup_userfaultfd_complete(). We do this by implementing a new function, dup_userfaultfd_fail(), which performs the same loop, only decrementing reference counts. Note that we perform mmgrab() on the parent and child mm's, however userfaultfd_ctx_put() will mmdrop() this once the reference count drops to zero, so we will avoid memory leaks correctly here. Link: https://lkml.kernel.org/r/cover.1729014377.git.lorenzo.stoakes@oracle.com Link: https://lkml.kernel.org/r/d3691d58bb58712b6fb3df2be441d175bd3cdf07.1729014377.git.lorenzo.stoakes@oracle.com Fixes: d24062914837 ("fork: use __mt_dup() to duplicate maple tree in dup_mmap()") Signed-off-by: Lorenzo Stoakes Reported-by: Jann Horn Reviewed-by: Jann Horn Reviewed-by: Liam R. Howlett Cc: Alexander Viro Cc: Christian Brauner Cc: Jan Kara Cc: Linus Torvalds Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton

posix-cpu-timers: Clear TICK_DEP_BIT_POSIX_TIMER on clone

2024-10-27T09:36:04Z

When cloning a new thread, its posix_cputimers are not inherited, and are cleared by posix_cputimers_init(). However, this does not clear the tick dependency it creates in tsk->tick_dep_mask, and the handler does not reach the code to clear the dependency if there were no timers to begin with. Thus if a thread has a cputimer running before clone/fork, all descendants will prevent nohz_full unless they create a cputimer of their own. Fix this by entirely clearing the tick_dep_mask in copy_process(). (There is currently no inherited state that needs a tick dependency) Process-wide timers do not have this problem because fork does not copy signal_struct as a baseline, it creates one from scratch. Fixes: b78783000d5c ("posix-cpu-timers: Migrate to use new tick dependency mask model") Signed-off-by: Ben Segall Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/xm26o737bq8o.fsf@google.com

close_range(): fix the logics in descriptor table trimming

2024-09-30T01:52:29Z

Cloning a descriptor table picks the size that would cover all currently opened files. That's fine for clone() and unshare(), but for close_range() there's an additional twist - we clone before we close, and it would be a shame to have close_range(3, ~0U, CLOSE_RANGE_UNSHARE) leave us with a huge descriptor table when we are not going to keep anything past stderr, just because some large file descriptor used to be open before our call has taken it out. Unfortunately, it had been dealt with in an inherently racy way - sane_fdtable_size() gets a "don't copy anything past that" argument (passed via unshare_fd() and dup_fd()), close_range() decides how much should be trimmed and passes that to unshare_fd(). The problem is, a range that used to extend to the end of descriptor table back when close_range() had looked at it might very well have stuff grown after it by the time dup_fd() has allocated a new files_struct and started to figure out the capacity of fdtable to be attached to that. That leads to interesting pathological cases; at the very least it's a QoI issue, since unshare(CLONE_FILES) is atomic in a sense that it takes a snapshot of descriptor table one might have observed at some point. Since CLOSE_RANGE_UNSHARE close_range() is supposed to be a combination of unshare(CLONE_FILES) with plain close_range(), ending up with a weird state that would never occur with unshare(2) is confusing, to put it mildly. It's not hard to get rid of - all it takes is passing both ends of the range down to sane_fdtable_size(). There we are under ->files_lock, so the race is trivially avoided. So we do the following: * switch close_files() from calling unshare_fd() to calling dup_fd(). * undo the calling convention change done to unshare_fd() in 60997c3d45d9 "close_range: add CLOSE_RANGE_UNSHARE" * introduce struct fd_range, pass a pointer to that to dup_fd() and sane_fdtable_size() instead of "trim everything past that point" they are currently getting. NULL means "we are not going to be punching any holes"; NR_OPEN_MAX is gone. * make sane_fdtable_size() use find_last_bit() instead of open-coding it; it's easier to follow that way. * while we are at it, have dup_fd() report errors by returning ERR_PTR(), no need to use a separate int *errorp argument. Fixes: 60997c3d45d9 "close_range: add CLOSE_RANGE_UNSHARE" Cc: stable@vger.kernel.org Signed-off-by: Al Viro

Merge tag 'memblock-v6.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock

2024-09-25T18:35:19Z

Pull memblock updates from Mike Rapoport: - new memblock_estimated_nr_free_pages() helper to replace totalram_pages() which is less accurate when CONFIG_DEFERRED_STRUCT_PAGE_INIT is set - fixes for memblock tests * tag 'memblock-v6.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock: s390/mm: get estimated free pages by memblock api kernel/fork.c: get estimated free pages by memblock api mm/memblock: introduce a new helper memblock_estimated_nr_free_pages() memblock test: fix implicit declaration of function 'strscpy' memblock test: fix implicit declaration of function 'isspace' memblock test: fix implicit declaration of function 'memparse' memblock test: add the definition of __setup() memblock test: fix implicit declaration of function 'virt_to_phys' tools/testing: abstract two init.h into common include directory memblock tests: include export.h in linkage.h as kernel dose memblock tests: include memory_hotplug.h in mmzone.h as kernel dose

Merge tag 'sched_ext-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

2024-09-21T16:44:57Z

Pull sched_ext support from Tejun Heo: "This implements a new scheduler class called ‘ext_sched_class’, or sched_ext, which allows scheduling policies to be implemented as BPF programs. The goals of this are: - Ease of experimentation and exploration: Enabling rapid iteration of new scheduling policies. - Customization: Building application-specific schedulers which implement policies that are not applicable to general-purpose schedulers. - Rapid scheduler deployments: Non-disruptive swap outs of scheduling policies in production environments" See individual commits for more documentation, but also the cover letter for the latest series: Link: https://lore.kernel.org/all/20240618212056.2833381-1-tj@kernel.org/ * tag 'sched_ext-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (110 commits) sched: Move update_other_load_avgs() to kernel/sched/pelt.c sched_ext: Don't trigger ops.quiescent/runnable() on migrations sched_ext: Synchronize bypass state changes with rq lock scx_qmap: Implement highpri boosting sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq() sched_ext: Compact struct bpf_iter_scx_dsq_kern sched_ext: Replace consume_local_task() with move_local_task_to_local_dsq() sched_ext: Move consume_local_task() upward sched_ext: Move sanity check and dsq_mod_nr() into task_unlink_from_dsq() sched_ext: Reorder args for consume_local/remote_task() sched_ext: Restructure dispatch_to_local_dsq() sched_ext: Fix processs_ddsp_deferred_locals() by unifying DTL_INVALID handling sched_ext: Make find_dsq_for_dispatch() handle SCX_DSQ_LOCAL_ON sched_ext: Refactor consume_remote_task() sched_ext: Rename scx_kfunc_set_sleepable to unlocked and relocate sched_ext: Add missing static to scx_dump_data sched_ext: Add missing static to scx_has_op[] sched_ext: Temporarily work around pick_task_scx() being called without balance_scx() sched_ext: Add a cgroup scheduler which uses flattened hierarchy sched_ext: Add cgroup support ...

Merge tag 'mm-stable-2024-09-20-02-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-09-21T14:29:05Z

Pull MM updates from Andrew Morton: "Along with the usual shower of singleton patches, notable patch series in this pull request are: - "Align kvrealloc() with krealloc()" from Danilo Krummrich. Adds consistency to the APIs and behaviour of these two core allocation functions. This also simplifies/enables Rustification. - "Some cleanups for shmem" from Baolin Wang. No functional changes - mode code reuse, better function naming, logic simplifications. - "mm: some small page fault cleanups" from Josef Bacik. No functional changes - code cleanups only. - "Various memory tiering fixes" from Zi Yan. A small fix and a little cleanup. - "mm/swap: remove boilerplate" from Yu Zhao. Code cleanups and simplifications and .text shrinkage. - "Kernel stack usage histogram" from Pasha Tatashin and Shakeel Butt. This is a feature, it adds new feilds to /proc/vmstat such as $ grep kstack /proc/vmstat kstack_1k 3 kstack_2k 188 kstack_4k 11391 kstack_8k 243 kstack_16k 0 which tells us that 11391 processes used 4k of stack while none at all used 16k. Useful for some system tuning things, but partivularly useful for "the dynamic kernel stack project". - "kmemleak: support for percpu memory leak detect" from Pavel Tikhomirov. Teaches kmemleak to detect leaksage of percpu memory. - "mm: memcg: page counters optimizations" from Roman Gushchin. "3 independent small optimizations of page counters". - "mm: split PTE/PMD PT table Kconfig cleanups+clarifications" from David Hildenbrand. Improves PTE/PMD splitlock detection, makes powerpc/8xx work correctly by design rather than by accident. - "mm: remove arch_make_page_accessible()" from David Hildenbrand. Some folio conversions which make arch_make_page_accessible() unneeded. - "mm, memcg: cg2 memory{.swap,}.peak write handlers" fro David Finkel. Cleans up and fixes our handling of the resetting of the cgroup/process peak-memory-use detector. - "Make core VMA operations internal and testable" from Lorenzo Stoakes. Rationalizaion and encapsulation of the VMA manipulation APIs. With a view to better enable testing of the VMA functions, even from a userspace-only harness. - "mm: zswap: fixes for global shrinker" from Takero Funaki. Fix issues in the zswap global shrinker, resulting in improved performance. - "mm: print the promo watermark in zoneinfo" from Kaiyang Zhao. Fill in some missing info in /proc/zoneinfo. - "mm: replace follow_page() by folio_walk" from David Hildenbrand. Code cleanups and rationalizations (conversion to folio_walk()) resulting in the removal of follow_page(). - "improving dynamic zswap shrinker protection scheme" from Nhat Pham. Some tuning to improve zswap's dynamic shrinker. Significant reductions in swapin and improvements in performance are shown. - "mm: Fix several issues with unaccepted memory" from Kirill Shutemov. Improvements to the new unaccepted memory feature, - "mm/mprotect: Fix dax puds" from Peter Xu. Implements mprotect on DAX PUDs. This was missing, although nobody seems to have notied yet. - "Introduce a store type enum for the Maple tree" from Sidhartha Kumar. Cleanups and modest performance improvements for the maple tree library code. - "memcg: further decouple v1 code from v2" from Shakeel Butt. Move more cgroup v1 remnants away from the v2 memcg code. - "memcg: initiate deprecation of v1 features" from Shakeel Butt. Adds various warnings telling users that memcg v1 features are deprecated. - "mm: swap: mTHP swap allocator base on swap cluster order" from Chris Li. Greatly improves the success rate of the mTHP swap allocation. - "mm: introduce numa_memblks" from Mike Rapoport. Moves various disparate per-arch implementations of numa_memblk code into generic code. - "mm: batch free swaps for zap_pte_range()" from Barry Song. Greatly improves the performance of munmap() of swap-filled ptes. - "support large folio swap-out and swap-in for shmem" from Baolin Wang. With this series we no longer split shmem large folios into simgle-page folios when swapping out shmem. - "mm/hugetlb: alloc/free gigantic folios" from Yu Zhao. Nice performance improvements and code reductions for gigantic folios. - "support shmem mTHP collapse" from Baolin Wang. Adds support for khugepaged's collapsing of shmem mTHP folios. - "mm: Optimize mseal checks" from Pedro Falcato. Fixes an mprotect() performance regression due to the addition of mseal(). - "Increase the number of bits available in page_type" from Matthew Wilcox. Increases the number of bits available in page_type! - "Simplify the page flags a little" from Matthew Wilcox. Many legacy page flags are now folio flags, so the page-based flags and their accessors/mutators can be removed. - "mm: store zero pages to be swapped out in a bitmap" from Usama Arif. An optimization which permits us to avoid writing/reading zero-filled zswap pages to backing store. - "Avoid MAP_FIXED gap exposure" from Liam Howlett. Fixes a race window which occurs when a MAP_FIXED operqtion is occurring during an unrelated vma tree walk. - "mm: remove vma_merge()" from Lorenzo Stoakes. Major rotorooting of the vma_merge() functionality, making ot cleaner, more testable and better tested. - "misc fixups for DAMON {self,kunit} tests" from SeongJae Park. Minor fixups of DAMON selftests and kunit tests. - "mm: memory_hotplug: improve do_migrate_range()" from Kefeng Wang. Code cleanups and folio conversions. - "Shmem mTHP controls and stats improvements" from Ryan Roberts. Cleanups for shmem controls and stats. - "mm: count the number of anonymous THPs per size" from Barry Song. Expose additional anon THP stats to userspace for improved tuning. - "mm: finish isolate/putback_lru_page()" from Kefeng Wang: more folio conversions and removal of now-unused page-based APIs. - "replace per-quota region priorities histogram buffer with per-context one" from SeongJae Park. DAMON histogram rationalization. - "Docs/damon: update GitHub repo URLs and maintainer-profile" from SeongJae Park. DAMON documentation updates. - "mm/vdpa: correct misuse of non-direct-reclaim __GFP_NOFAIL and improve related doc and warn" from Jason Wang: fixes usage of page allocator __GFP_NOFAIL and GFP_ATOMIC flags. - "mm: split underused THPs" from Yu Zhao. Improve THP=always policy. This was overprovisioning THPs in sparsely accessed memory areas. - "zram: introduce custom comp backends API" frm Sergey Senozhatsky. Add support for zram run-time compression algorithm tuning. - "mm: Care about shadow stack guard gap when getting an unmapped area" from Mark Brown. Fix up the various arch_get_unmapped_area() implementations to better respect guard areas. - "Improve mem_cgroup_iter()" from Kinsey Ho. Improve the reliability of mem_cgroup_iter() and various code cleanups. - "mm: Support huge pfnmaps" from Peter Xu. Extends the usage of huge pfnmap support. - "resource: Fix region_intersects() vs add_memory_driver_managed()" from Huang Ying. Fix a bug in region_intersects() for systems with CXL memory. - "mm: hwpoison: two more poison recovery" from Kefeng Wang. Teaches a couple more code paths to correctly recover from the encountering of poisoned memry. - "mm: enable large folios swap-in support" from Barry Song. Support the swapin of mTHP memory into appropriately-sized folios, rather than into single-page folios" * tag 'mm-stable-2024-09-20-02-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (416 commits) zram: free secondary algorithms names uprobes: turn xol_area->pages[2] into xol_area->page uprobes: introduce the global struct vm_special_mapping xol_mapping Revert "uprobes: use vm_special_mapping close() functionality" mm: support large folios swap-in for sync io devices mm: add nr argument in mem_cgroup_swapin_uncharge_swap() helper to support large folios mm: fix swap_read_folio_zeromap() for large folios with partial zeromap mm/debug_vm_pgtable: Use pxdp_get() for accessing page table entries set_memory: add __must_check to generic stubs mm/vma: return the exact errno in vms_gather_munmap_vmas() memcg: cleanup with !CONFIG_MEMCG_V1 mm/show_mem.c: report alloc tags in human readable units mm: support poison recovery from copy_present_page() mm: support poison recovery from do_cow_fault() resource, kunit: add test case for region_intersects() resource: make alloc_free_mem_region() works for iomem_resource mm: z3fold: deprecate CONFIG_Z3FOLD vfio/pci: implement huge_fault support mm/arm64: support large pfn mappings mm/x86: support large pfn mappings ...

Merge tag 'cgroup-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2024-09-18T04:39:03Z

Pull cgroup updates from Tejun Heo: - cpuset isolation improvements - cpuset cgroup1 support is split into its own file behind the new config option CONFIG_CPUSET_V1. This makes it the second controller which makes cgroup1 support optional after memcg - Handling of unavailable v1 controller handling improved during cgroup1 mount operations - union_find applied to cpuset. It makes code simpler and more efficient - Reduce spurious events in pids.events - Cleanups and other misc changes - Contains a merge of cgroup/for-6.11-fixes to receive cpuset fixes that further changes build upon * tag 'cgroup-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (34 commits) cgroup: Do not report unavailable v1 controllers in /proc/cgroups cgroup: Disallow mounting v1 hierarchies without controller implementation cgroup/cpuset: Expose cpuset filesystem with cpuset v1 only cgroup/cpuset: Move cpu.h include to cpuset-internal.h cgroup/cpuset: add sefltest for cpuset v1 cgroup/cpuset: guard cpuset-v1 code under CONFIG_CPUSETS_V1 cgroup/cpuset: rename functions shared between v1 and v2 cgroup/cpuset: move v1 interfaces to cpuset-v1.c cgroup/cpuset: move validate_change_legacy to cpuset-v1.c cgroup/cpuset: move legacy hotplug update to cpuset-v1.c cgroup/cpuset: add callback_lock helper cgroup/cpuset: move memory_spread to cpuset-v1.c cgroup/cpuset: move relax_domain_level to cpuset-v1.c cgroup/cpuset: move memory_pressure to cpuset-v1.c cgroup/cpuset: move common code to cpuset-internal.h cgroup/cpuset: introduce cpuset-v1.c selftest/cgroup: Make test_cpuset_prs.sh deal with pre-isolated CPUs cgroup/cpuset: Account for boot time isolated CPUs cgroup/cpuset: remove use_parent_ecpus of cpuset cgroup/cpuset: remove fetch_xcpus ...