Re: [syzbot] KASAN: invalid-access Read in copy_page

[Andrey Konovalov]

Hi Catalin,

Syzbot reported an issue with MTE tagging of user pages, see the report below.

Possibly, it's related to your "mm: kasan: Skip unpoisoning of user
pages" series. However, I'm not sure what the issue is.

Do you have any ideas?

Thanks!

On Sat, Aug 6, 2022 at 3:31 AM syzbot
<syzbot+c2c79c6d6eddc5262b77@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    9e2f40233670 Merge tag 'x86_sgx_for_v6.0-2022-08-03.1' of ..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16181cbc080000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=886e7348b2982e4d
> dashboard link: https://syzkaller.appspot.com/bug?extid=c2c79c6d6eddc5262b77
> compiler:       aarch64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: arm64
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+c2c79c6d6eddc5262b77@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ==================================================================
> BUG: KASAN: invalid-access in copy_page+0x10/0xd0 arch/arm64/lib/copy_page.S:26
> Read at addr f5ff000017f2e000 by task syz-executor.1/2218
> Pointer tag: [f5], memory tag: [f2]
>
> CPU: 1 PID: 2218 Comm: syz-executor.1 Not tainted 5.19.0-syzkaller-10532-g9e2f40233670 #0
> Hardware name: linux,dummy-virt (DT)
> Call trace:
>  dump_backtrace.part.0+0xcc/0xe0 arch/arm64/kernel/stacktrace.c:182
>  dump_backtrace arch/arm64/kernel/stacktrace.c:188 [inline]
>  show_stack+0x18/0x5c arch/arm64/kernel/stacktrace.c:189
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0x68/0x84 lib/dump_stack.c:106
>  print_address_description mm/kasan/report.c:313 [inline]
>  print_report+0xfc/0x5f0 mm/kasan/report.c:429
>  kasan_report+0x8c/0xb0 mm/kasan/report.c:491
>  __do_kernel_fault+0x104/0x1c0 arch/arm64/mm/fault.c:319
>  do_bad_area arch/arm64/mm/fault.c:469 [inline]
>  do_tag_check_fault+0x78/0x90 arch/arm64/mm/fault.c:738
>  do_mem_abort+0x48/0xa0 arch/arm64/mm/fault.c:814
>  el1_abort+0x40/0x60 arch/arm64/kernel/entry-common.c:366
>  el1h_64_sync_handler+0xb0/0xd0 arch/arm64/kernel/entry-common.c:417
>  el1h_64_sync+0x64/0x68 arch/arm64/kernel/entry.S:576
>  copy_page+0x10/0xd0 arch/arm64/lib/copy_page.S:26
>  copy_user_highpage+0x18/0x4c arch/arm64/mm/copypage.c:34
>  __wp_page_copy_user mm/memory.c:2848 [inline]
>  wp_page_copy+0xa0/0x790 mm/memory.c:3109
>  do_wp_page+0x150/0x6a4 mm/memory.c:3471
>  handle_pte_fault mm/memory.c:4925 [inline]
>  __handle_mm_fault+0x6c4/0xf84 mm/memory.c:5046
>  handle_mm_fault+0xe8/0x25c mm/memory.c:5144
>  __do_page_fault arch/arm64/mm/fault.c:502 [inline]
>  do_page_fault+0x140/0x3b0 arch/arm64/mm/fault.c:602
>  do_mem_abort+0x48/0xa0 arch/arm64/mm/fault.c:814
>  el0_da+0x48/0xbc arch/arm64/kernel/entry-common.c:502
>  el0t_64_sync_handler+0x134/0x1b0 arch/arm64/kernel/entry-common.c:645
>  el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:581
>
> The buggy address belongs to the physical page:
> page:000000003e6672be refcount:3 mapcount:2 mapping:0000000000000000 index:0xffffffffe pfn:0x57f2e
> memcg:fbff00001ded8000
> anon flags: 0x1ffc2800208001c(uptodate|dirty|lru|swapbacked|arch_2|node=0|zone=0|lastcpupid=0x7ff|kasantag=0xa)
> raw: 01ffc2800208001c fffffc00004f91c8 fcff00001d1b1000 f1ff00000510b231
> raw: 0000000ffffffffe 0000000000000000 0000000300000001 fbff00001ded8000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff000017f2de00: f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5
>  ffff000017f2df00: f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5
> >ffff000017f2e000: f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2
>                    ^
>  ffff000017f2e100: f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2
>  ffff000017f2e200: f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2
> ==================================================================
>
>
> ---
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>
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