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Patch series "kasan, slub: reset tag when printing address", v3. With hardware tag-based kasan enabled, we reset the tag when we access metadata to avoid from false alarm. This patch (of 2): Kmemleak needs to scan kernel memory to check memory leak. With hardware tag-based kasan enabled, when it scans on the invalid slab and dereference, the issue will occur as below. Hardware tag-based KASAN doesn't use compiler instrumentation, we can not use kasan_disable_current() to ignore tag check. Based on the below report, there are 11 0xf7 granules, which amounts to 176 bytes, and the object is allocated from the kmalloc-256 cache. So when kmemleak accesses the last 256-176 bytes, it causes faults, as those are marked with KASAN_KMALLOC_REDZONE == KASAN_TAG_INVALID == 0xfe. Thus, we reset tags before accessing metadata to avoid from false positives. BUG: KASAN: out-of-bounds in scan_block+0x58/0x170 Read at addr f7ff0000c0074eb0 by task kmemleak/138 Pointer tag: [f7], memory tag: [fe] CPU: 7 PID: 138 Comm: kmemleak Not tainted 5.14.0-rc2-00001-g8cae8cd89f05-dirty #134 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x0/0x1b0 show_stack+0x1c/0x30 dump_stack_lvl+0x68/0x84 print_address_description+0x7c/0x2b4 kasan_report+0x138/0x38c __do_kernel_fault+0x190/0x1c4 do_tag_check_fault+0x78/0x90 do_mem_abort+0x44/0xb4 el1_abort+0x40/0x60 el1h_64_sync_handler+0xb4/0xd0 el1h_64_sync+0x78/0x7c scan_block+0x58/0x170 scan_gray_list+0xdc/0x1a0 kmemleak_scan+0x2ac/0x560 kmemleak_scan_thread+0xb0/0xe0 kthread+0x154/0x160 ret_from_fork+0x10/0x18 Allocated by task 0: kasan_save_stack+0x2c/0x60 __kasan_kmalloc+0xec/0x104 __kmalloc+0x224/0x3c4 __register_sysctl_paths+0x200/0x290 register_sysctl_table+0x2c/0x40 sysctl_init+0x20/0x34 proc_sys_init+0x3c/0x48 proc_root_init+0x80/0x9c start_kernel+0x648/0x6a4 __primary_switched+0xc0/0xc8 Freed by task 0: kasan_save_stack+0x2c/0x60 kasan_set_track+0x2c/0x40 kasan_set_free_info+0x44/0x54 ____kasan_slab_free.constprop.0+0x150/0x1b0 __kasan_slab_free+0x14/0x20 slab_free_freelist_hook+0xa4/0x1fc kfree+0x1e8/0x30c put_fs_context+0x124/0x220 vfs_kern_mount.part.0+0x60/0xd4 kern_mount+0x24/0x4c bdev_cache_init+0x70/0x9c vfs_caches_init+0xdc/0xf4 start_kernel+0x638/0x6a4 __primary_switched+0xc0/0xc8 The buggy address belongs to the object at ffff0000c0074e00 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 176 bytes inside of 256-byte region [ffff0000c0074e00, ffff0000c0074f00) The buggy address belongs to the page: page:(____ptrval____) refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x100074 head:(____ptrval____) order:2 compound_mapcount:0 compound_pincount:0 flags: 0xbfffc0000010200(slab|head|node=0|zone=2|lastcpupid=0xffff|kasantag=0x0) raw: 0bfffc0000010200 0000000000000000 dead000000000122 f5ff0000c0002300 raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff0000c0074c00: f0 f0 f0 f0 f0 f0 f0 f0 f0 fe fe fe fe fe fe fe ffff0000c0074d00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe >ffff0000c0074e00: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 fe fe fe fe fe ^ ffff0000c0074f00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe ffff0000c0075000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Disabling lock debugging due to kernel taint kmemleak: 181 new suspected memory leaks (see /sys/kernel/debug/kmemleak) Link: https://lkml.kernel.org/r/20210804090957.12393-1-Kuan-Ying.Lee@mediatek.com Link: https://lkml.kernel.org/r/20210804090957.12393-2-Kuan-Ying.Lee@mediatek.com Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Marco Elver <elver@google.com> Cc: Nicholas Tang <nicholas.tang@mediatek.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Chinwen Chang <chinwen.chang@mediatek.com> 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.