linux, branch v6.15

Linux 6.15

2025-05-25T23:09:23Z

Disable FOP_DONTCACHE for now due to bugs

2025-05-25T22:43:36Z

This is kind of last-minute, but Al Viro reported that the new FOP_DONTCACHE flag causes memory corruption due to use-after-free issues. This was triggered by commit 974c5e6139db ("xfs: flag as supporting FOP_DONTCACHE"), but that is not the underlying bug - it is just the first user of the flag. Vlastimil Babka suspects the underlying problem stems from the folio_end_writeback() logic introduced in commit fb7d3bc414939 ("mm/filemap: drop streaming/uncached pages when writeback completes"). The most straightforward fix would be to just revert the commit that exposed this, but Matthew Wilcox points out that other filesystems are also starting to enable the FOP_DONTCACHE logic, so this instead disables that bit globally for now. The fix will hopefully end up being trivial and we can just re-enable this logic after more testing, but until such a time we'll have to disable the new FOP_DONTCACHE flag. Reported-by: Al Viro Link: https://lore.kernel.org/all/20250525083209.GS2023217@ZenIV/ Triggered-by: 974c5e6139db ("xfs: flag as supporting FOP_DONTCACHE") Cc: Vlastimil Babka Cc: Matthew Wilcox Cc: Jan Kara Cc: Jens Axboe Cc: Christoph Hellwig Cc: Darrick J. Wong Cc: Christian Brauner Signed-off-by: Linus Torvalds

Merge tag 'mm-hotfixes-stable-2025-05-25-00-58' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-05-25T14:48:35Z

Pull hotfixes from Andrew Morton: "22 hotfixes. 13 are cc:stable and the remainder address post-6.14 issues or aren't considered necessary for -stable kernels. 19 are for MM" * tag 'mm-hotfixes-stable-2025-05-25-00-58' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (22 commits) mailmap: add Jarkko's employer email address mm: fix copy_vma() error handling for hugetlb mappings memcg: always call cond_resched() after fn() mm/hugetlb: fix kernel NULL pointer dereference when replacing free hugetlb folios mm: vmalloc: only zero-init on vrealloc shrink mm: vmalloc: actually use the in-place vrealloc region alloc_tag: allocate percpu counters for module tags dynamically module: release codetag section when module load fails mm/cma: make detection of highmem_start more robust MAINTAINERS: add mm memory policy section MAINTAINERS: add mm ksm section kasan: avoid sleepable page allocation from atomic context highmem: add folio_test_partial_kmap() MAINTAINERS: add hung-task detector section taskstats: fix struct taskstats breaks backward compatibility since version 15 mm/truncate: fix out-of-bounds when doing a right-aligned split MAINTAINERS: add mm reclaim section MAINTAINERS: update page allocator section mm: fix VM_UFFD_MINOR == VM_SHADOW_STACK on USERFAULTFD=y && ARM64_GCS=y mm: mmap: map MAP_STACK to VM_NOHUGEPAGE only if THP is enabled ...

mailmap: add Jarkko's employer email address

2025-05-25T07:53:49Z

Add the current employer email address to mailmap. Link: https://lkml.kernel.org/r/20250523121105.15850-1-jarkko@kernel.org Signed-off-by: Jarkko Sakkinen Cc: Alexander Sverdlin Cc: Antonio Quartulli Cc: Carlos Bilbao Cc: Kees Cook Cc: Simon Wunderlich Signed-off-by: Andrew Morton

mm: fix copy_vma() error handling for hugetlb mappings

2025-05-25T07:53:49Z

If, during a mremap() operation for a hugetlb-backed memory mapping, copy_vma() fails after the source vma has been duplicated and opened (ie. vma_link() fails), the error is handled by closing the new vma. This updates the hugetlbfs reservation counter of the reservation map which at this point is referenced by both the source vma and the new copy. As a result, once the new vma has been freed and copy_vma() returns, the reservation counter for the source vma will be incorrect. This patch addresses this corner case by clearing the hugetlb private page reservation reference for the new vma and decrementing the reference before closing the vma, so that vma_close() won't update the reservation counter. This is also what copy_vma_and_data() does with the source vma if copy_vma() succeeds, so a helper function has been added to do the fixup in both functions. The issue was reported by a private syzbot instance and can be reproduced using the C reproducer in [1]. It's also a possible duplicate of public syzbot report [2]. The WARNING report is: ============================================================ page_counter underflow: -1024 nr_pages=1024 WARNING: CPU: 0 PID: 3287 at mm/page_counter.c:61 page_counter_cancel+0xf6/0x120 Modules linked in: CPU: 0 UID: 0 PID: 3287 Comm: repro__WARNING_ Not tainted 6.15.0-rc7+ #54 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-2-gc13ff2cd-prebuilt.qemu.org 04/01/2014 RIP: 0010:page_counter_cancel+0xf6/0x120 Code: ff 5b 41 5e 41 5f 5d c3 cc cc cc cc e8 f3 4f 8f ff c6 05 64 01 27 06 01 48 c7 c7 60 15 f8 85 48 89 de 4c 89 fa e8 2a a7 51 ff <0f> 0b e9 66 ff ff ff 44 89 f9 80 e1 07 38 c1 7c 9d 4c 81 RSP: 0018:ffffc900025df6a0 EFLAGS: 00010246 RAX: 2edfc409ebb44e00 RBX: fffffffffffffc00 RCX: ffff8880155f0000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: dffffc0000000000 R08: ffffffff81c4a23c R09: 1ffff1100330482a R10: dffffc0000000000 R11: ffffed100330482b R12: 0000000000000000 R13: ffff888058a882c0 R14: ffff888058a882c0 R15: 0000000000000400 FS: 0000000000000000(0000) GS:ffff88808fc53000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004b33e0 CR3: 00000000076d6000 CR4: 00000000000006f0 Call Trace: page_counter_uncharge+0x33/0x80 hugetlb_cgroup_uncharge_counter+0xcb/0x120 hugetlb_vm_op_close+0x579/0x960 ? __pfx_hugetlb_vm_op_close+0x10/0x10 remove_vma+0x88/0x130 exit_mmap+0x71e/0xe00 ? __pfx_exit_mmap+0x10/0x10 ? __mutex_unlock_slowpath+0x22e/0x7f0 ? __pfx_exit_aio+0x10/0x10 ? __up_read+0x256/0x690 ? uprobe_clear_state+0x274/0x290 ? mm_update_next_owner+0xa9/0x810 __mmput+0xc9/0x370 exit_mm+0x203/0x2f0 ? __pfx_exit_mm+0x10/0x10 ? taskstats_exit+0x32b/0xa60 do_exit+0x921/0x2740 ? do_raw_spin_lock+0x155/0x3b0 ? __pfx_do_exit+0x10/0x10 ? __pfx_do_raw_spin_lock+0x10/0x10 ? _raw_spin_lock_irq+0xc5/0x100 do_group_exit+0x20c/0x2c0 get_signal+0x168c/0x1720 ? __pfx_get_signal+0x10/0x10 ? schedule+0x165/0x360 arch_do_signal_or_restart+0x8e/0x7d0 ? __pfx_arch_do_signal_or_restart+0x10/0x10 ? __pfx___se_sys_futex+0x10/0x10 syscall_exit_to_user_mode+0xb8/0x2c0 do_syscall_64+0x75/0x120 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x422dcd Code: Unable to access opcode bytes at 0x422da3. RSP: 002b:00007ff266cdb208 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: 0000000000000001 RBX: 00007ff266cdbcdc RCX: 0000000000422dcd RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00000000004c7bec RBP: 00007ff266cdb220 R08: 203a6362696c6720 R09: 203a6362696c6720 R10: 0000200000c00000 R11: 0000000000000246 R12: ffffffffffffffd0 R13: 0000000000000002 R14: 00007ffe1cb5f520 R15: 00007ff266cbb000 ============================================================ Link: https://lkml.kernel.org/r/20250523-warning_in_page_counter_cancel-v2-1-b6df1a8cfefd@igalia.com Link: https://people.igalia.com/rcn/kernel_logs/20250422__WARNING_in_page_counter_cancel__repro.c [1] Link: https://lore.kernel.org/all/67000a50.050a0220.49194.048d.GAE@google.com/ [2] Signed-off-by: Ricardo Cañuelo Navarro Suggested-by: Lorenzo Stoakes Reviewed-by: Liam R. Howlett Cc: Florent Revest Cc: Jann Horn Cc: Oscar Salvador Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton

memcg: always call cond_resched() after fn()

2025-05-25T07:53:49Z

I am seeing soft lockup on certain machine types when a cgroup OOMs. This is happening because killing the process in certain machine might be very slow, which causes the soft lockup and RCU stalls. This happens usually when the cgroup has MANY processes and memory.oom.group is set. Example I am seeing in real production: [462012.244552] Memory cgroup out of memory: Killed process 3370438 (crosvm) .... .... [462037.318059] Memory cgroup out of memory: Killed process 4171372 (adb) .... [462037.348314] watchdog: BUG: soft lockup - CPU#64 stuck for 26s! [stat_manager-ag:1618982] .... Quick look at why this is so slow, it seems to be related to serial flush for certain machine types. For all the crashes I saw, the target CPU was at console_flush_all(). In the case above, there are thousands of processes in the cgroup, and it is soft locking up before it reaches the 1024 limit in the code (which would call the cond_resched()). So, cond_resched() in 1024 blocks is not sufficient. Remove the counter-based conditional rescheduling logic and call cond_resched() unconditionally after each task iteration, after fn() is called. This avoids the lockup independently of how slow fn() is. Link: https://lkml.kernel.org/r/20250523-memcg_fix-v1-1-ad3eafb60477@debian.org Fixes: ade81479c7dd ("memcg: fix soft lockup in the OOM process") Signed-off-by: Breno Leitao Suggested-by: Rik van Riel Acked-by: Shakeel Butt Cc: Michael van der Westhuizen Cc: Usama Arif Cc: Pavel Begunkov Cc: Chen Ridong Cc: Greg Kroah-Hartman Cc: Johannes Weiner Cc: Michal Hocko Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Signed-off-by: Andrew Morton

mm/hugetlb: fix kernel NULL pointer dereference when replacing free hugetlb folios

2025-05-25T07:53:48Z

A kernel crash was observed when replacing free hugetlb folios: BUG: kernel NULL pointer dereference, address: 0000000000000028 PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 28 UID: 0 PID: 29639 Comm: test_cma.sh Tainted 6.15.0-rc6-zp #41 PREEMPT(voluntary) RIP: 0010:alloc_and_dissolve_hugetlb_folio+0x1d/0x1f0 RSP: 0018:ffffc9000b30fa90 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000342cca RCX: ffffea0043000000 RDX: ffffc9000b30fb08 RSI: ffffea0043000000 RDI: 0000000000000000 RBP: ffffc9000b30fb20 R08: 0000000000001000 R09: 0000000000000000 R10: ffff88886f92eb00 R11: 0000000000000000 R12: ffffea0043000000 R13: 0000000000000000 R14: 00000000010c0200 R15: 0000000000000004 FS: 00007fcda5f14740(0000) GS:ffff8888ec1d8000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000028 CR3: 0000000391402000 CR4: 0000000000350ef0 Call Trace: replace_free_hugepage_folios+0xb6/0x100 alloc_contig_range_noprof+0x18a/0x590 ? srso_return_thunk+0x5/0x5f ? down_read+0x12/0xa0 ? srso_return_thunk+0x5/0x5f cma_range_alloc.constprop.0+0x131/0x290 __cma_alloc+0xcf/0x2c0 cma_alloc_write+0x43/0xb0 simple_attr_write_xsigned.constprop.0.isra.0+0xb2/0x110 debugfs_attr_write+0x46/0x70 full_proxy_write+0x62/0xa0 vfs_write+0xf8/0x420 ? srso_return_thunk+0x5/0x5f ? filp_flush+0x86/0xa0 ? srso_return_thunk+0x5/0x5f ? filp_close+0x1f/0x30 ? srso_return_thunk+0x5/0x5f ? do_dup2+0xaf/0x160 ? srso_return_thunk+0x5/0x5f ksys_write+0x65/0xe0 do_syscall_64+0x64/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e There is a potential race between __update_and_free_hugetlb_folio() and replace_free_hugepage_folios(): CPU1 CPU2 __update_and_free_hugetlb_folio replace_free_hugepage_folios folio_test_hugetlb(folio) -- It's still hugetlb folio. __folio_clear_hugetlb(folio) hugetlb_free_folio(folio) h = folio_hstate(folio) -- Here, h is NULL pointer When the above race condition occurs, folio_hstate(folio) returns NULL, and subsequent access to this NULL pointer will cause the system to crash. To resolve this issue, execute folio_hstate(folio) under the protection of the hugetlb_lock lock, ensuring that folio_hstate(folio) does not return NULL. Link: https://lkml.kernel.org/r/1747884137-26685-1-git-send-email-yangge1116@126.com Fixes: 04f13d241b8b ("mm: replace free hugepage folios after migration") Signed-off-by: Ge Yang Reviewed-by: Muchun Song Reviewed-by: Oscar Salvador Cc: Baolin Wang Cc: Barry Song <21cnbao@gmail.com> Cc: David Hildenbrand Cc: Signed-off-by: Andrew Morton

mm: vmalloc: only zero-init on vrealloc shrink

2025-05-25T07:53:48Z

The common case is to grow reallocations, and since init_on_alloc will have already zeroed the whole allocation, we only need to zero when shrinking the allocation. Link: https://lkml.kernel.org/r/20250515214217.619685-2-kees@kernel.org Fixes: a0309faf1cb0 ("mm: vmalloc: support more granular vrealloc() sizing") Signed-off-by: Kees Cook Tested-by: Pawan Gupta Cc: Danilo Krummrich Cc: Eduard Zingerman Cc: "Erhard F." Cc: Shung-Hsi Yu Cc: "Uladzislau Rezki (Sony)" Cc: Signed-off-by: Andrew Morton

mm: vmalloc: actually use the in-place vrealloc region

2025-05-25T07:53:48Z

Patch series "mm: vmalloc: Actually use the in-place vrealloc region". This fixes a performance regression[1] with vrealloc()[1]. The refactoring to not build a new vmalloc region only actually worked when shrinking. Actually return the resized area when it grows. Ugh. Link: https://lkml.kernel.org/r/20250515214217.619685-1-kees@kernel.org Fixes: a0309faf1cb0 ("mm: vmalloc: support more granular vrealloc() sizing") Signed-off-by: Kees Cook Reported-by: Shung-Hsi Yu Closes: https://lore.kernel.org/all/20250515-bpf-verifier-slowdown-vwo2meju4cgp2su5ckj@6gi6ssxbnfqg [1] Tested-by: Eduard Zingerman Tested-by: Pawan Gupta Tested-by: Shung-Hsi Yu Reviewed-by: "Uladzislau Rezki (Sony)" Reviewed-by: Danilo Krummrich Cc: "Erhard F." Cc: Signed-off-by: Andrew Morton

alloc_tag: allocate percpu counters for module tags dynamically

2025-05-25T07:53:48Z

When a module gets unloaded it checks whether any of its tags are still in use and if so, we keep the memory containing module's allocation tags alive until all tags are unused. However percpu counters referenced by the tags are freed by free_module(). This will lead to UAF if the memory allocated by a module is accessed after module was unloaded. To fix this we allocate percpu counters for module allocation tags dynamically and we keep it alive for tags which are still in use after module unloading. This also removes the requirement of a larger PERCPU_MODULE_RESERVE when memory allocation profiling is enabled because percpu memory for counters does not need to be reserved anymore. Link: https://lkml.kernel.org/r/20250517000739.5930-1-surenb@google.com Fixes: 0db6f8d7820a ("alloc_tag: load module tags into separate contiguous memory") Signed-off-by: Suren Baghdasaryan Reported-by: David Wang <00107082@163.com> Closes: https://lore.kernel.org/all/20250516131246.6244-1-00107082@163.com/ Tested-by: David Wang <00107082@163.com> Cc: Christoph Lameter (Ampere) Cc: Dennis Zhou Cc: Kent Overstreet Cc: Pasha Tatashin Cc: Tejun Heo Cc: Signed-off-by: Andrew Morton