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Date:   Mon, 24 Apr 2023 00:21:45 -0700
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Subject: [syzbot] [mm?] [fs?] KCSAN: data-race in __filemap_remove_folio / shmem_get_folio_gfp
From:   syzbot <syzbot+ec4650f158c91a963120@syzkaller.appspotmail.com>
To:     akpm@linux-foundation.org, hughd@google.com,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, syzkaller-bugs@googlegroups.com
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Hello,

syzbot found the following issue on:

HEAD commit:    cb0856346a60 Merge tag 'mm-hotfixes-stable-2023-04-19-16-3..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=170802cfc80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa4baf7c6b35b5d5
dashboard link: https://syzkaller.appspot.com/bug?extid=ec4650f158c91a963120
compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a02dd7789fb2/disk-cb085634.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a1a1eac454f6/vmlinux-cb085634.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bb0447014913/bzImage-cb085634.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ec4650f158c91a963120@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __filemap_remove_folio / shmem_get_folio_gfp

read-write to 0xffff888136bf8960 of 8 bytes by task 19402 on cpu 1:
 page_cache_delete mm/filemap.c:147 [inline]
 __filemap_remove_folio+0x22f/0x330 mm/filemap.c:225
 filemap_remove_folio+0x6c/0x220 mm/filemap.c:257
 truncate_inode_folio+0x19f/0x1e0 mm/truncate.c:196
 shmem_undo_range+0x24d/0xc20 mm/shmem.c:942
 shmem_truncate_range mm/shmem.c:1041 [inline]
 shmem_fallocate+0x2fc/0x8d0 mm/shmem.c:2779
 vfs_fallocate+0x369/0x3d0 fs/open.c:324
 madvise_remove mm/madvise.c:1001 [inline]
 madvise_vma_behavior mm/madvise.c:1025 [inline]
 madvise_walk_vmas mm/madvise.c:1260 [inline]
 do_madvise+0x77b/0x28a0 mm/madvise.c:1439
 __do_sys_madvise mm/madvise.c:1452 [inline]
 __se_sys_madvise mm/madvise.c:1450 [inline]
 __x64_sys_madvise+0x60/0x70 mm/madvise.c:1450
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888136bf8960 of 8 bytes by task 19400 on cpu 0:
 shmem_recalc_inode mm/shmem.c:359 [inline]
 shmem_get_folio_gfp+0xc0a/0x1120 mm/shmem.c:1977
 shmem_fault+0xd9/0x3d0 mm/shmem.c:2152
 __do_fault mm/memory.c:4155 [inline]
 do_read_fault mm/memory.c:4506 [inline]
 do_fault mm/memory.c:4635 [inline]
 handle_pte_fault mm/memory.c:4923 [inline]
 __handle_mm_fault mm/memory.c:5065 [inline]
 handle_mm_fault+0x115d/0x21d0 mm/memory.c:5211
 faultin_page mm/gup.c:925 [inline]
 __get_user_pages+0x363/0xc30 mm/gup.c:1147
 populate_vma_page_range mm/gup.c:1543 [inline]
 __mm_populate+0x23a/0x360 mm/gup.c:1652
 mm_populate include/linux/mm.h:3026 [inline]
 vm_mmap_pgoff+0x174/0x210 mm/util.c:547
 ksys_mmap_pgoff+0xc5/0x320 mm/mmap.c:1410
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000437 -> 0x0000000000000430

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 19400 Comm: syz-executor.3 Not tainted 6.3.0-rc7-syzkaller-00089-gcb0856346a60 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
==================================================================


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