Re: [syzbot] [mm?] KCSAN: data-race in generic_fillattr / shmem_mknod (2)

[syzbot <syzbot+702361cf7e3d95758761@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KCSAN: data-race in ext4_mb_regular_allocator / mb_mark_used

==================================================================
BUG: KCSAN: data-race in ext4_mb_regular_allocator / mb_mark_used

read-write to 0xffff888100696014 of 4 bytes by task 3404 on cpu 0:
 mb_mark_used+0x128/0xb40 fs/ext4/mballoc.c:2065
 ext4_mb_use_best_found+0xf6/0x2a0 fs/ext4/mballoc.c:2147
 ext4_mb_check_limits fs/ext4/mballoc.c:2211 [inline]
 ext4_mb_complex_scan_group+0x7a7/0x800 fs/ext4/mballoc.c:2527
 ext4_mb_regular_allocator+0x10d4/0x2590 fs/ext4/mballoc.c:2941
 ext4_mb_new_blocks+0x801/0x2020 fs/ext4/mballoc.c:6219
 ext4_ext_map_blocks+0x1070/0x3640 fs/ext4/extents.c:4318
 ext4_map_blocks+0x72a/0xf50 fs/ext4/inode.c:652
 ext4_getblk+0x112/0x500 fs/ext4/inode.c:862
 ext4_bread+0x2c/0x110 fs/ext4/inode.c:918
 ext4_append+0x164/0x2a0 fs/ext4/namei.c:83
 ext4_init_new_dir+0x17b/0x510 fs/ext4/namei.c:2979
 ext4_mkdir+0x313/0x740 fs/ext4/namei.c:3025
 vfs_mkdir+0x1f4/0x320 fs/namei.c:4257
 do_mkdirat+0x12f/0x2a0 fs/namei.c:4280
 __do_sys_mkdirat fs/namei.c:4295 [inline]
 __se_sys_mkdirat fs/namei.c:4293 [inline]
 __x64_sys_mkdirat+0x4e/0x60 fs/namei.c:4293
 x64_sys_call+0x2cd3/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:259
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x54/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

read to 0xffff888100696014 of 4 bytes by task 3444 on cpu 1:
 ext4_mb_good_group_nolock fs/ext4/mballoc.c:2666 [inline]
 ext4_mb_regular_allocator+0x948/0x2590 fs/ext4/mballoc.c:2903
 ext4_mb_new_blocks+0x801/0x2020 fs/ext4/mballoc.c:6219
 ext4_ext_map_blocks+0x1070/0x3640 fs/ext4/extents.c:4318
 ext4_map_blocks+0x72a/0xf50 fs/ext4/inode.c:652
 ext4_getblk+0x112/0x500 fs/ext4/inode.c:862
 ext4_bread+0x2c/0x110 fs/ext4/inode.c:918
 ext4_append+0x164/0x2a0 fs/ext4/namei.c:83
 ext4_init_new_dir+0x17b/0x510 fs/ext4/namei.c:2979
 ext4_mkdir+0x313/0x740 fs/ext4/namei.c:3025
 vfs_mkdir+0x1f4/0x320 fs/namei.c:4257
 do_mkdirat+0x12f/0x2a0 fs/namei.c:4280
 __do_sys_mkdirat fs/namei.c:4295 [inline]
 __se_sys_mkdirat fs/namei.c:4293 [inline]
 __x64_sys_mkdirat+0x4e/0x60 fs/namei.c:4293
 x64_sys_call+0x2cd3/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:259
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x54/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

value changed: 0x000005ca -> 0x000005c9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3444 Comm: syz-executor.5 Not tainted 6.11.0-syzkaller-04557-g2f27fce67173-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
==================================================================


Tested on:

commit:         2f27fce6 Merge tag 'sound-6.12-rc1' of git://git.kerne..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1353bfc7980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dac6637d61966e53
dashboard link: https://syzkaller.appspot.com/bug?extid=702361cf7e3d95758761
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=14fcc69f980000