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6c82d45c7f
We hit this issue in our internal test. When enabling generic kasan, a kfree()'d object is put into per-cpu quarantine first. If the cpu goes offline, object still remains in the per-cpu quarantine. If we call kmem_cache_destroy() now, slub will report "Objects remaining" error. ============================================================================= BUG test_module_slab (Not tainted): Objects remaining in test_module_slab on __kmem_cache_shutdown() ----------------------------------------------------------------------------- Disabling lock debugging due to kernel taint INFO: Slab 0x(____ptrval____) objects=34 used=1 fp=0x(____ptrval____) flags=0x2ffff00000010200 CPU: 3 PID: 176 Comm: cat Tainted: G B 5.10.0-rc1-00007-g4525c8781ec0-dirty #10 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x0/0x2b0 show_stack+0x18/0x68 dump_stack+0xfc/0x168 slab_err+0xac/0xd4 __kmem_cache_shutdown+0x1e4/0x3c8 kmem_cache_destroy+0x68/0x130 test_version_show+0x84/0xf0 module_attr_show+0x40/0x60 sysfs_kf_seq_show+0x128/0x1c0 kernfs_seq_show+0xa0/0xb8 seq_read+0x1f0/0x7e8 kernfs_fop_read+0x70/0x338 vfs_read+0xe4/0x250 ksys_read+0xc8/0x180 __arm64_sys_read+0x44/0x58 el0_svc_common.constprop.0+0xac/0x228 do_el0_svc+0x38/0xa0 el0_sync_handler+0x170/0x178 el0_sync+0x174/0x180 INFO: Object 0x(____ptrval____) @offset=15848 INFO: Allocated in test_version_show+0x98/0xf0 age=8188 cpu=6 pid=172 stack_trace_save+0x9c/0xd0 set_track+0x64/0xf0 alloc_debug_processing+0x104/0x1a0 ___slab_alloc+0x628/0x648 __slab_alloc.isra.0+0x2c/0x58 kmem_cache_alloc+0x560/0x588 test_version_show+0x98/0xf0 module_attr_show+0x40/0x60 sysfs_kf_seq_show+0x128/0x1c0 kernfs_seq_show+0xa0/0xb8 seq_read+0x1f0/0x7e8 kernfs_fop_read+0x70/0x338 vfs_read+0xe4/0x250 ksys_read+0xc8/0x180 __arm64_sys_read+0x44/0x58 el0_svc_common.constprop.0+0xac/0x228 kmem_cache_destroy test_module_slab: Slab cache still has objects Register a cpu hotplug function to remove all objects in the offline per-cpu quarantine when cpu is going offline. Set a per-cpu variable to indicate this cpu is offline. [qiang.zhang@windriver.com: fix slab double free when cpu-hotplug] Link: https://lkml.kernel.org/r/20201204102206.20237-1-qiang.zhang@windriver.com Link: https://lkml.kernel.org/r/1606895585-17382-2-git-send-email-Kuan-Ying.Lee@mediatek.com Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> Signed-off-by: Zqiang <qiang.zhang@windriver.com> Suggested-by: Dmitry Vyukov <dvyukov@google.com> Reported-by: Guangye Yang <guangye.yang@mediatek.com> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Matthias Brugger <matthias.bgg@gmail.com> Cc: Nicholas Tang <nicholas.tang@mediatek.com> Cc: Miles Chen <miles.chen@mediatek.com> Cc: Qian Cai <qcai@redhat.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.