kernel.git/fs/coredump.c, branch linux-6.10.y

Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

2024-05-23T19:04:36Z

Pull virtio updates from Michael Tsirkin: "Several new features here: - virtio-net is finally supported in vduse - virtio (balloon and mem) interaction with suspend is improved - vhost-scsi now handles signals better/faster And fixes, cleanups all over the place" * tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost: (48 commits) virtio-pci: Check if is_avq is NULL virtio: delete vq in vp_find_vqs_msix() when request_irq() fails MAINTAINERS: add Eugenio Pérez as reviewer vhost-vdpa: Remove usage of the deprecated ida_simple_xx() API vp_vdpa: don't allocate unused msix vectors sound: virtio: drop owner assignment fuse: virtio: drop owner assignment scsi: virtio: drop owner assignment rpmsg: virtio: drop owner assignment nvdimm: virtio_pmem: drop owner assignment wifi: mac80211_hwsim: drop owner assignment vsock/virtio: drop owner assignment net: 9p: virtio: drop owner assignment net: virtio: drop owner assignment net: caif: virtio: drop owner assignment misc: nsm: drop owner assignment iommu: virtio: drop owner assignment drm/virtio: drop owner assignment gpio: virtio: drop owner assignment firmware: arm_scmi: virtio: drop owner assignment ...

kernel: Remove signal hacks for vhost_tasks

2024-05-22T12:31:15Z

This removes the signal/coredump hacks added for vhost_tasks in: Commit f9010dbdce91 ("fork, vhost: Use CLONE_THREAD to fix freezer/ps regression") When that patch was added vhost_tasks did not handle SIGKILL and would try to ignore/clear the signal and continue on until the device's close function was called. In the previous patches vhost_tasks and the vhost drivers were converted to support SIGKILL by cleaning themselves up and exiting. The hacks are no longer needed so this removes them. Signed-off-by: Mike Christie Message-Id: <20240316004707.45557-10-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin

fs/coredump: Enable dynamic configuration of max file note size

2024-05-08T16:53:00Z

Introduce the capability to dynamically configure the maximum file note size for ELF core dumps via sysctl. Why is this being done? We have observed that during a crash when there are more than 65k mmaps in memory, the existing fixed limit on the size of the ELF notes section becomes a bottleneck. The notes section quickly reaches its capacity, leading to incomplete memory segment information in the resulting coredump. This truncation compromises the utility of the coredumps, as crucial information about the memory state at the time of the crash might be omitted. This enhancement removes the previous static limit of 4MB, allowing system administrators to adjust the size based on system-specific requirements or constraints. Eg: $ sysctl -a | grep core_file_note_size_limit kernel.core_file_note_size_limit = 4194304 $ sysctl -n kernel.core_file_note_size_limit 4194304 $echo 519304 > /proc/sys/kernel/core_file_note_size_limit $sysctl -n kernel.core_file_note_size_limit 519304 Attempting to write beyond the ceiling value of 16MB $echo 17194304 > /proc/sys/kernel/core_file_note_size_limit bash: echo: write error: Invalid argument Signed-off-by: Vijay Nag Signed-off-by: Allen Pais Link: https://lore.kernel.org/r/20240506193700.7884-1-apais@linux.microsoft.com Signed-off-by: Kees Cook

iov_iter: get rid of 'copy_mc' flag

2024-03-06T09:52:12Z

This flag is only set by one single user: the magical core dumping code that looks up user pages one by one, and then writes them out using their kernel addresses (by using a BVEC_ITER). That actually ends up being a huge problem, because while we do use copy_mc_to_kernel() for this case and it is able to handle the possible machine checks involved, nothing else is really ready to handle the failures caused by the machine check. In particular, as reported by Tong Tiangen, we don't actually support fault_in_iov_iter_readable() on a machine check area. As a result, the usual logic for writing things to a file under a filesystem lock, which involves doing a copy with page faults disabled and then if that fails trying to fault pages in without holding the locks with fault_in_iov_iter_readable() does not work at all. We could decide to always just make the MC copy "succeed" (and filling the destination with zeroes), and that would then create a core dump file that just ignores any machine checks. But honestly, this single special case has been problematic before, and means that all the normal iov_iter code ends up slightly more complex and slower. See for example commit c9eec08bac96 ("iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc()") where David Howells re-organized the code just to avoid having to check the 'copy_mc' flags inside the inner iov_iter loops. So considering that we have exactly one user, and that one user is a non-critical special case that doesn't actually ever trigger in real life (Tong found this with manual error injection), the sane solution is to just decide that the onus on handling the machine check lines on that user instead. Ergo, do the copy_mc_to_kernel() in the core dump logic itself, copying the user data to a stable kernel page before writing it out. Fixes: f1982740f5e7 ("iov_iter: Convert iterate*() to inline funcs") Signed-off-by: Linus Torvalds Signed-off-by: Tong Tiangen Link: https://lore.kernel.org/r/20240305133336.3804360-1-tongtiangen@huawei.com Link: https://lore.kernel.org/all/4e80924d-9c85-f13a-722a-6a5d2b1c225a@huawei.com/ Tested-by: David Howells Reviewed-by: David Howells Reviewed-by: Jens Axboe Reported-by: Tong Tiangen Signed-off-by: Christian Brauner

fs: Remove the now superfluous sentinel elements from ctl_table array

2023-12-28T12:57:57Z

This commit comes at the tail end of a greater effort to remove the empty elements at the end of the ctl_table arrays (sentinels) which will reduce the overall build time size of the kernel and run time memory bloat by ~64 bytes per sentinel (further information Link : https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/) Remove sentinel elements ctl_table struct. Special attention was placed in making sure that an empty directory for fs/verity was created when CONFIG_FS_VERITY_BUILTIN_SIGNATURES is not defined. In this case we use the register sysctl call that expects a size. Signed-off-by: Joel Granados Reviewed-by: Jan Kara Reviewed-by: "Darrick J. Wong" Acked-by: Christian Brauner Signed-off-by: Luis Chamberlain

Merge tag 'v6.5/vfs.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2023-06-26T16:50:21Z

Pull misc vfs updates from Christian Brauner: "Miscellaneous features, cleanups, and fixes for vfs and individual fs Features: - Use mode 0600 for file created by cachefilesd so it can be run by unprivileged users. This aligns them with directories which are already created with mode 0700 by cachefilesd - Reorder a few members in struct file to prevent some false sharing scenarios - Indicate that an eventfd is used a semaphore in the eventfd's fdinfo procfs file - Add a missing uapi header for eventfd exposing relevant uapi defines - Let the VFS protect transitions of a superblock from read-only to read-write in addition to the protection it already provides for transitions from read-write to read-only. Protecting read-only to read-write transitions allows filesystems such as ext4 to perform internal writes, keeping writers away until the transition is completed Cleanups: - Arnd removed the architecture specific arch_report_meminfo() prototypes and added a generic one into procfs.h. Note, we got a report about a warning in amdpgpu codepaths that suggested this was bisectable to this change but we concluded it was a false positive - Remove unused parameters from split_fs_names() - Rename put_and_unmap_page() to unmap_and_put_page() to let the name reflect the order of the cleanup operation that has to unmap before the actual put - Unexport buffer_check_dirty_writeback() as it is not used outside of block device aops - Stop allocating aio rings from highmem - Protecting read-{only,write} transitions in the VFS used open-coded barriers in various places. Replace them with proper little helpers and document both the helpers and all barrier interactions involved when transitioning between read-{only,write} states - Use flexible array members in old readdir codepaths Fixes: - Use the correct type __poll_t for epoll and eventfd - Replace all deprecated strlcpy() invocations, whose return value isn't checked with an equivalent strscpy() call - Fix some kernel-doc warnings in fs/open.c - Reduce the stack usage in jffs2's xattr codepaths finally getting rid of this: fs/jffs2/xattr.c:887:1: error: the frame size of 1088 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] royally annoying compilation warning - Use __FMODE_NONOTIFY instead of FMODE_NONOTIFY where an int and not fmode_t is required to avoid fmode_t to integer degradation warnings - Create coredumps with O_WRONLY instead of O_RDWR. There's a long explanation in that commit how O_RDWR is actually a bug which we found out with the help of Linus and git archeology - Fix "no previous prototype" warnings in the pipe codepaths - Add overflow calculations for remap_verify_area() as a signed addition overflow could be triggered in xfstests - Fix a null pointer dereference in sysv - Use an unsigned variable for length calculations in jfs avoiding compilation warnings with gcc 13 - Fix a dangling pipe pointer in the watch queue codepath - The legacy mount option parser provided as a fallback by the VFS for filesystems not yet converted to the new mount api did prefix the generated mount option string with a leading ',' causing issues for some filesystems - Fix a repeated word in a comment in fs.h - autofs: Update the ctime when mtime is updated as mandated by POSIX" * tag 'v6.5/vfs.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (27 commits) readdir: Replace one-element arrays with flexible-array members fs: Provide helpers for manipulating sb->s_readonly_remount fs: Protect reconfiguration of sb read-write from racing writes eventfd: add a uapi header for eventfd userspace APIs autofs: set ctime as well when mtime changes on a dir eventfd: show the EFD_SEMAPHORE flag in fdinfo fs/aio: Stop allocating aio rings from HIGHMEM fs: Fix comment typo fs: unexport buffer_check_dirty_writeback fs: avoid empty option when generating legacy mount string watch_queue: prevent dangling pipe pointer fs.h: Optimize file struct to prevent false sharing highmem: Rename put_and_unmap_page() to unmap_and_put_page() cachefiles: Allow the cache to be non-root init: remove unused names parameter in split_fs_names() jfs: Use unsigned variable for length calculations fs/sysv: Null check to prevent null-ptr-deref bug fs: use UB-safe check for signed addition overflow in remap_verify_area procfs: consolidate arch_report_meminfo declaration fs: pipe: reveal missing function protoypes ...

fork, vhost: Use CLONE_THREAD to fix freezer/ps regression

2023-06-01T21:15:33Z

When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman Co-developed-by: Mike Christie Signed-off-by: Mike Christie Acked-by: Michael S. Tsirkin Signed-off-by: Linus Torvalds

coredump: require O_WRONLY instead of O_RDWR

2023-05-17T07:13:44Z

The motivation for this patch has been to enable using a stricter apparmor profile to prevent programs from reading any coredump in the system. However, this became something else. The following details are based on Christian's and Linus' archeology into the history of the number "2" in the coredump handling code. To make sure we're not accidently introducing some subtle behavioral change into the coredump code we set out on a voyage into the depths of history.git to figure out why this was O_RDWR in the first place. Coredump handling was introduced over 30 years ago in commit ddc733f452e0 ("[PATCH] Linux-0.97 (August 1, 1992)"). The original code used O_WRONLY: open_namei("core",O_CREAT | O_WRONLY | O_TRUNC,0600,&inode,NULL) However, this changed in 1993 and starting with commit 9cb9f18b5d26 ("[PATCH] Linux-0.99.10 (June 7, 1993)") the coredump code suddenly used the constant "2": open_namei("core",O_CREAT | 2 | O_TRUNC,0600,&inode,NULL) This was curious as in the same commit the kernel switched from constants to proper defines in other places such as KERNEL_DS and USER_DS and O_RDWR did already exist. So why was "2" used? It turns out that open_namei() - an early version of what later turned into filp_open() - didn't accept O_RDWR. A semantic quirk of the open() uapi is the definition of the O_RDONLY flag. It would seem natural to define: #define O_RDWR (O_RDONLY | O_WRONLY) but that isn't possible because: #define O_RDONLY 0 This makes O_RDONLY effectively meaningless when passed to the kernel. In other words, there has never been a way - until O_PATH at least - to open a file without any permission; O_RDONLY was always implied on the uapi side while the kernel does in fact allow opening files without permissions. The trouble comes when trying to map the uapi flags onto the corresponding file mode flags FMODE_{READ,WRITE}. This mapping still happens today and is causing issues to this day (We ran into this during additions for openat2() for example.). So the special value "3" was used to indicate that the file was opened for special access: f->f_flags = flag = flags; f->f_mode = (flag+1) & O_ACCMODE; if (f->f_mode) flag++; This allowed the file mode to be set to FMODE_READ | FMODE_WRITE mapping the O_{RDONLY,WRONLY,RDWR} flags into the FMODE_{READ,WRITE} flags. The special access then required read-write permissions and 0 was used to access symlinks. But back when ddc733f452e0 ("[PATCH] Linux-0.97 (August 1, 1992)") added coredump handling open_namei() took the FMODE_{READ,WRITE} flags as an argument. So the coredump handling introduced in ddc733f452e0 ("[PATCH] Linux-0.97 (August 1, 1992)") was buggy because O_WRONLY shouldn't have been passed. Since O_WRONLY is 1 but open_namei() took FMODE_{READ,WRITE} it was passed FMODE_READ on accident. So 9cb9f18b5d26 ("[PATCH] Linux-0.99.10 (June 7, 1993)") was a bugfix for this and the 2 didn't really mean O_RDWR, it meant FMODE_WRITE which was correct. The clue is that FMODE_{READ,WRITE} didn't exist yet and thus a raw "2" value was passed. Fast forward 5 years when around 2.2.4pre4 (February 16, 1999) this code was changed to: - dentry = open_namei(corefile,O_CREAT | 2 | O_TRUNC | O_NOFOLLOW, 0600); ... + file = filp_open(corefile,O_CREAT | 2 | O_TRUNC | O_NOFOLLOW, 0600); At this point the raw "2" should have become O_WRONLY again as filp_open() didn't take FMODE_{READ,WRITE} but O_{RDONLY,WRONLY,RDWR}. Another 17 years later, the code was changed again cementing the mistake and making it almost impossible to detect when commit 378c6520e7d2 ("fs/coredump: prevent fsuid=0 dumps into user-controlled directories") replaced the raw "2" with O_RDWR. And now, here we are with this patch that sent us on a quest to answer the big questions in life such as "Why are coredump files opened with O_RDWR?" and "Is it safe to just use O_WRONLY?". So with this commit we're reintroducing O_WRONLY again and bringing this code back to its original state when it was first introduced in commit ddc733f452e0 ("[PATCH] Linux-0.97 (August 1, 1992)") over 30 years ago. Signed-off-by: Vladimir Sementsov-Ogievskiy Message-Id: <20230420120409.602576-1-vsementsov@yandex-team.ru> [brauner@kernel.org: completely rewritten commit message] Signed-off-by: Linus Torvalds Signed-off-by: Christian Brauner

mm: hwpoison: coredump: support recovery from dump_user_range()

2023-05-03T00:21:50Z

dump_user_range() is used to copy the user page to a coredump file, but if a hardware memory error occurred during copy, which called from __kernel_write_iter() in dump_user_range(), it crashes, CPU: 112 PID: 7014 Comm: mca-recover Not tainted 6.3.0-rc2 #425 pc : __memcpy+0x110/0x260 lr : _copy_from_iter+0x3bc/0x4c8 ... Call trace: __memcpy+0x110/0x260 copy_page_from_iter+0xcc/0x130 pipe_write+0x164/0x6d8 __kernel_write_iter+0x9c/0x210 dump_user_range+0xc8/0x1d8 elf_core_dump+0x308/0x368 do_coredump+0x2e8/0xa40 get_signal+0x59c/0x788 do_signal+0x118/0x1f8 do_notify_resume+0xf0/0x280 el0_da+0x130/0x138 el0t_64_sync_handler+0x68/0xc0 el0t_64_sync+0x188/0x190 Generally, the '->write_iter' of file ops will use copy_page_from_iter() and copy_page_from_iter_atomic(), change memcpy() to copy_mc_to_kernel() in both of them to handle #MC during source read, which stop coredump processing and kill the task instead of kernel panic, but the source address may not always a user address, so introduce a new copy_mc flag in struct iov_iter{} to indicate that the iter could do a safe memory copy, also introduce the helpers to set/cleck the flag, for now, it's only used in coredump's dump_user_range(), but it could expand to any other scenarios to fix the similar issue. Link: https://lkml.kernel.org/r/20230417045323.11054-1-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang Cc: Alexander Viro Cc: Christian Brauner Cc: Miaohe Lin Cc: Naoya Horiguchi Cc: Tong Tiangen Cc: Jens Axboe Signed-off-by: Andrew Morton

Merge tag 'mm-stable-2023-02-20-13-37' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2023-02-24T01:09:35Z

Pull MM updates from Andrew Morton: - Daniel Verkamp has contributed a memfd series ("mm/memfd: add F_SEAL_EXEC") which permits the setting of the memfd execute bit at memfd creation time, with the option of sealing the state of the X bit. - Peter Xu adds a patch series ("mm/hugetlb: Make huge_pte_offset() thread-safe for pmd unshare") which addresses a rare race condition related to PMD unsharing. - Several folioification patch serieses from Matthew Wilcox, Vishal Moola, Sidhartha Kumar and Lorenzo Stoakes - Johannes Weiner has a series ("mm: push down lock_page_memcg()") which does perform some memcg maintenance and cleanup work. - SeongJae Park has added DAMOS filtering to DAMON, with the series "mm/damon/core: implement damos filter". These filters provide users with finer-grained control over DAMOS's actions. SeongJae has also done some DAMON cleanup work. - Kairui Song adds a series ("Clean up and fixes for swap"). - Vernon Yang contributed the series "Clean up and refinement for maple tree". - Yu Zhao has contributed the "mm: multi-gen LRU: memcg LRU" series. It adds to MGLRU an LRU of memcgs, to improve the scalability of global reclaim. - David Hildenbrand has added some userfaultfd cleanup work in the series "mm: uffd-wp + change_protection() cleanups". - Christoph Hellwig has removed the generic_writepages() library function in the series "remove generic_writepages". - Baolin Wang has performed some maintenance on the compaction code in his series "Some small improvements for compaction". - Sidhartha Kumar is doing some maintenance work on struct page in his series "Get rid of tail page fields". - David Hildenbrand contributed some cleanup, bugfixing and generalization of pte management and of pte debugging in his series "mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on all architectures with swap PTEs". - Mel Gorman and Neil Brown have removed the __GFP_ATOMIC allocation flag in the series "Discard __GFP_ATOMIC". - Sergey Senozhatsky has improved zsmalloc's memory utilization with his series "zsmalloc: make zspage chain size configurable". - Joey Gouly has added prctl() support for prohibiting the creation of writeable+executable mappings. The previous BPF-based approach had shortcomings. See "mm: In-kernel support for memory-deny-write-execute (MDWE)". - Waiman Long did some kmemleak cleanup and bugfixing in the series "mm/kmemleak: Simplify kmemleak_cond_resched() & fix UAF". - T.J. Alumbaugh has contributed some MGLRU cleanup work in his series "mm: multi-gen LRU: improve". - Jiaqi Yan has provided some enhancements to our memory error statistics reporting, mainly by presenting the statistics on a per-node basis. See the series "Introduce per NUMA node memory error statistics". - Mel Gorman has a second and hopefully final shot at fixing a CPU-hog regression in compaction via his series "Fix excessive CPU usage during compaction". - Christoph Hellwig does some vmalloc maintenance work in the series "cleanup vfree and vunmap". - Christoph Hellwig has removed block_device_operations.rw_page() in ths series "remove ->rw_page". - We get some maple_tree improvements and cleanups in Liam Howlett's series "VMA tree type safety and remove __vma_adjust()". - Suren Baghdasaryan has done some work on the maintainability of our vm_flags handling in the series "introduce vm_flags modifier functions". - Some pagemap cleanup and generalization work in Mike Rapoport's series "mm, arch: add generic implementation of pfn_valid() for FLATMEM" and "fixups for generic implementation of pfn_valid()" - Baoquan He has done some work to make /proc/vmallocinfo and /proc/kcore better represent the real state of things in his series "mm/vmalloc.c: allow vread() to read out vm_map_ram areas". - Jason Gunthorpe rationalized the GUP system's interface to the rest of the kernel in the series "Simplify the external interface for GUP". - SeongJae Park wishes to migrate people from DAMON's debugfs interface over to its sysfs interface. To support this, we'll temporarily be printing warnings when people use the debugfs interface. See the series "mm/damon: deprecate DAMON debugfs interface". - Andrey Konovalov provided the accurately named "lib/stackdepot: fixes and clean-ups" series. - Huang Ying has provided a dramatic reduction in migration's TLB flush IPI rates with the series "migrate_pages(): batch TLB flushing". - Arnd Bergmann has some objtool fixups in "objtool warning fixes". * tag 'mm-stable-2023-02-20-13-37' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (505 commits) include/linux/migrate.h: remove unneeded externs mm/memory_hotplug: cleanup return value handing in do_migrate_range() mm/uffd: fix comment in handling pte markers mm: change to return bool for isolate_movable_page() mm: hugetlb: change to return bool for isolate_hugetlb() mm: change to return bool for isolate_lru_page() mm: change to return bool for folio_isolate_lru() objtool: add UACCESS exceptions for __tsan_volatile_read/write kmsan: disable ftrace in kmsan core code kasan: mark addr_has_metadata __always_inline mm: memcontrol: rename memcg_kmem_enabled() sh: initialize max_mapnr m68k/nommu: add missing definition of ARCH_PFN_OFFSET mm: percpu: fix incorrect size in pcpu_obj_full_size() maple_tree: reduce stack usage with gcc-9 and earlier mm: page_alloc: call panic() when memoryless node allocation fails mm: multi-gen LRU: avoid futile retries migrate_pages: move THP/hugetlb migration support check to simplify code migrate_pages: batch flushing TLB migrate_pages: share more code between _unmap and _move ...