Re: [syzbot] [bcachefs?] KMSAN: uninit-value in bch2_copygc

From: syzbot
Date: Sun Nov 10 2024 - 19:55:03 EST


Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KMSAN: uninit-value in bch2_copygc

=====================================================
BUG: KMSAN: uninit-value in rht_ptr_rcu include/linux/rhashtable.h:376 [inline]
BUG: KMSAN: uninit-value in __rhashtable_lookup include/linux/rhashtable.h:607 [inline]
BUG: KMSAN: uninit-value in rhashtable_lookup include/linux/rhashtable.h:646 [inline]
BUG: KMSAN: uninit-value in rhashtable_lookup_fast include/linux/rhashtable.h:672 [inline]
BUG: KMSAN: uninit-value in bucket_in_flight fs/bcachefs/movinggc.c:145 [inline]
BUG: KMSAN: uninit-value in bch2_copygc_get_buckets fs/bcachefs/movinggc.c:171 [inline]
BUG: KMSAN: uninit-value in bch2_copygc+0x1d3f/0x58f0 fs/bcachefs/movinggc.c:222
rht_ptr_rcu include/linux/rhashtable.h:376 [inline]
__rhashtable_lookup include/linux/rhashtable.h:607 [inline]
rhashtable_lookup include/linux/rhashtable.h:646 [inline]
rhashtable_lookup_fast include/linux/rhashtable.h:672 [inline]
bucket_in_flight fs/bcachefs/movinggc.c:145 [inline]
bch2_copygc_get_buckets fs/bcachefs/movinggc.c:171 [inline]
bch2_copygc+0x1d3f/0x58f0 fs/bcachefs/movinggc.c:222
bch2_copygc_thread+0x83a/0xff0 fs/bcachefs/movinggc.c:383
kthread+0x3e2/0x540 kernel/kthread.c:389
ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Local variable b205.i created at:
bch2_copygc_get_buckets fs/bcachefs/movinggc.c:171 [inline]
bch2_copygc+0x15b3/0x58f0 fs/bcachefs/movinggc.c:222
bch2_copygc_thread+0x83a/0xff0 fs/bcachefs/movinggc.c:383

CPU: 1 UID: 0 PID: 6672 Comm: bch-copygc/loop Not tainted 6.12.0-rc7-syzkaller-g2d5404caa8c7-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
=====================================================
Kernel panic - not syncing: kmsan.panic set ...
CPU: 1 UID: 0 PID: 6672 Comm: bch-copygc/loop Tainted: G B 6.12.0-rc7-syzkaller-g2d5404caa8c7-dirty #0
Tainted: [B]=BAD_PAGE
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x216/0x2d0 lib/dump_stack.c:120
dump_stack+0x1e/0x30 lib/dump_stack.c:129
panic+0x4e2/0xcf0 kernel/panic.c:354
kmsan_report+0x2c7/0x2d0 mm/kmsan/report.c:218
__msan_warning+0x95/0x120 mm/kmsan/instrumentation.c:318
rht_ptr_rcu include/linux/rhashtable.h:376 [inline]
__rhashtable_lookup include/linux/rhashtable.h:607 [inline]
rhashtable_lookup include/linux/rhashtable.h:646 [inline]
rhashtable_lookup_fast include/linux/rhashtable.h:672 [inline]
bucket_in_flight fs/bcachefs/movinggc.c:145 [inline]
bch2_copygc_get_buckets fs/bcachefs/movinggc.c:171 [inline]
bch2_copygc+0x1d3f/0x58f0 fs/bcachefs/movinggc.c:222
bch2_copygc_thread+0x83a/0xff0 fs/bcachefs/movinggc.c:383
kthread+0x3e2/0x540 kernel/kthread.c:389
ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
Kernel Offset: disabled
Rebooting in 86400 seconds..


Tested on:

commit: 2d5404ca Linux 6.12-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=115e135f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=dcca673786a14715
dashboard link: https://syzkaller.appspot.com/bug?extid=8689d10f1894eedf774d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch: https://syzkaller.appspot.com/x/patch.diff?x=168608c0580000