syzbot


KCSAN: data-race in __fat_write_inode / fat12_ent_get

Status: fixed on 2020/07/17 17:58
Subsystems: exfat
[Documentation on labels]
Reported-by: syzbot+6f1624f937d9d6911e2d@syzkaller.appspotmail.com
Fix commit: b1b65750b8db fat: don't allow to mount if the FAT length == 0
First crash: 1583d, last: 1538d
Discussions (14)
Title Replies (including bot) Last reply
[PATCH 4.9 000/128] 4.9.228-rc1 review 135 (135) 2021/02/26 19:09
[PATCH 5.4 000/134] 5.4.47-rc1 review 141 (141) 2021/01/28 17:06
[PATCH 4.19 000/267] 4.19.129-rc1 review 280 (280) 2020/06/30 01:36
[PATCH 4.14 000/190] 4.14.185-rc1 review 197 (197) 2020/06/26 07:05
[PATCH AUTOSEL 4.14 001/108] power: supply: bq24257_charger: Replace depends on REGMAP_I2C with select 113 (113) 2020/06/23 18:59
[PATCH AUTOSEL 4.19 001/172] power: supply: bq24257_charger: Replace depends on REGMAP_I2C with select 175 (175) 2020/06/23 15:35
[PATCH AUTOSEL 4.4 01/60] clk: sunxi: Fix incorrect usage of round_down() 65 (65) 2020/06/22 00:07
[PATCH 4.4 000/101] 4.4.228-rc1 review 109 (109) 2020/06/20 15:06
[PATCH AUTOSEL 4.9 01/80] power: supply: bq24257_charger: Replace depends on REGMAP_I2C with select 81 (81) 2020/06/18 01:34
[PATCH 5.6 000/161] 5.6.19-rc1 review 164 (164) 2020/06/16 17:11
[PATCH 5.7 000/163] 5.7.3-rc1 review 164 (164) 2020/06/16 15:35
[patch 090/127] fat: don't allow to mount if the FAT length == 0 1 (1) 2020/06/04 23:50
[PATCH] fat: Don't allow to mount if the FAT length == 0 1 (1) 2020/04/07 13:10
KCSAN: data-race in __fat_write_inode / fat12_ent_get 5 (6) 2020/04/07 13:03

Sample crash report:
FAT-fs (loop1): error, clusters badly computed (876 != 875)
FAT-fs (loop1): error, clusters badly computed (877 != 876)
FAT-fs (loop1): error, clusters badly computed (878 != 877)
==================================================================
BUG: KCSAN: data-race in __fat_write_inode / fat12_ent_get

write to 0xffff8881015f423c of 4 bytes by task 9966 on cpu 1:
 __fat_write_inode+0x246/0x510 fs/fat/inode.c:877
 fat_write_inode+0x67/0xe0 fs/fat/inode.c:909
 write_inode fs/fs-writeback.c:1312 [inline]
 __writeback_single_inode+0x722/0x910 fs/fs-writeback.c:1511
 writeback_single_inode+0x219/0x2f0 fs/fs-writeback.c:1565
 sync_inode fs/fs-writeback.c:2602 [inline]
 sync_inode_metadata+0x75/0xa0 fs/fs-writeback.c:2622
 __generic_file_fsync+0x117/0x180 fs/libfs.c:1081
 fat_file_fsync+0x54/0x120 fs/fat/file.c:190
 vfs_fsync_range+0x7c/0x150 fs/sync.c:197
 generic_write_sync include/linux/fs.h:2867 [inline]
 generic_file_write_iter+0x31c/0x38e mm/filemap.c:3452
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x4a7/0x5d0 fs/read_write.c:693
 do_iter_write fs/read_write.c:998 [inline]
 do_iter_write+0x137/0x3a0 fs/read_write.c:979
 vfs_iter_write+0x56/0x80 fs/read_write.c:1039
 iter_file_splice_write+0x530/0x830 fs/splice.c:760
 do_splice_from fs/splice.c:863 [inline]
 direct_splice_actor+0x97/0xb0 fs/splice.c:1037
 splice_direct_to_actor+0x22f/0x540 fs/splice.c:992
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x396/0x810 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1575 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0xb8/0x140 fs/read_write.c:1567
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881015f423d of 1 bytes by task 9960 on cpu 0:
 fat12_ent_get+0x5e/0x120 fs/fat/fatent.c:125
 fat_ent_read+0x3de/0x560 fs/fat/fatent.c:370
 fat_get_cluster+0x52b/0x920 fs/fat/cache.c:266
 fat_bmap_cluster fs/fat/cache.c:299 [inline]
 fat_get_mapped_cluster+0x105/0x230 fs/fat/cache.c:320
 fat_bmap+0x146/0x28e fs/fat/cache.c:384
 __fat_get_block fs/fat/inode.c:165 [inline]
 fat_get_block+0x244/0x4f0 fs/fat/inode.c:190
 __block_write_begin_int+0x306/0xf80 fs/buffer.c:2008
 __block_write_begin fs/buffer.c:2058 [inline]
 block_write_begin+0x76/0x160 fs/buffer.c:2117
 cont_write_begin+0x3bd/0x660 fs/buffer.c:2466
 fat_write_begin+0x69/0xc0 fs/fat/inode.c:236
 pagecache_write_begin+0x67/0x90 mm/filemap.c:3106
 cont_expand_zero fs/buffer.c:2393 [inline]
 cont_write_begin+0x176/0x660 fs/buffer.c:2456
 fat_write_begin+0x69/0xc0 fs/fat/inode.c:236
 generic_perform_write+0x13a/0x320 mm/filemap.c:3287
 __generic_file_write_iter+0x240/0x370 mm/filemap.c:3416
 generic_file_write_iter+0x294/0x38e mm/filemap.c:3448
 call_write_iter include/linux/fs.h:1901 [inline]
 new_sync_write+0x303/0x400 fs/read_write.c:483
 __vfs_write+0x9e/0xb0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x189/0x380 fs/read_write.c:542
 ksys_write+0xc5/0x1a0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x49/0x60 fs/read_write.c:620
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9960 Comm: syz-executor.1 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/03/28 03:08 https://github.com/google/ktsan.git kcsan 40959e34d670 831e9a81 .config console log report ci2-upstream-kcsan-gce
2020/02/12 05:58 https://github.com/google/ktsan.git kcsan f60f0f543333 a75b198c .config console log report ci2-upstream-kcsan-gce
* Struck through repros no longer work on HEAD.