[syzbot] [bcachefs?] KMSAN: uninit-value in __bch2_alloc_v4_to_text

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    e04c78d86a96 Linux 6.16-rc2
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16fdc90c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=db26f33438d76de9
dashboard link: https://syzkaller.appspot.com/bug?extid=8eb51728519f6659ef7b
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11fdc90c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132995d4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c0f064a5f302/disk-e04c78d8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b71205c143e3/vmlinux-e04c78d8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2abdee22b79e/bzImage-e04c78d8.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/3838d178b843/mount_2.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8eb51728519f6659ef7b@xxxxxxxxxxxxxxxxxxxxxxxxx

    cached_sectors       0
    stripe               0
    stripe_redundancy    0
    io_time[READ]        1
    io_time[WRITE]       1024
    fragmentation     0
    bp_start          7
  
  incorrectly set at freespace:0:37:0 (free 0, genbits 0 should be 0), fixing
=====================================================
BUG: KMSAN: uninit-value in __bch2_alloc_v4_to_text+0x7a4/0xdf0 fs/bcachefs/alloc_background.c:355
 __bch2_alloc_v4_to_text+0x7a4/0xdf0 fs/bcachefs/alloc_background.c:355
 bch2_alloc_v4_to_text+0x181/0x1f0 fs/bcachefs/alloc_background.c:380
 bch2_val_to_text fs/bcachefs/bkey_methods.c:321 [inline]
 bch2_bkey_val_to_text+0x1e8/0x280 fs/bcachefs/bkey_methods.c:331
 bch2_check_discard_freespace_key+0xe35/0x1a30 fs/bcachefs/alloc_background.c:1436
 try_alloc_bucket fs/bcachefs/alloc_foreground.c:272 [inline]
 bch2_bucket_alloc_freelist fs/bcachefs/alloc_foreground.c:420 [inline]
 bch2_bucket_alloc_trans+0x225d/0x3a40 fs/bcachefs/alloc_foreground.c:544
 bch2_bucket_alloc_set_trans+0xebb/0x1c10 fs/bcachefs/alloc_foreground.c:728
 __open_bucket_add_buckets+0x21f8/0x37b0 fs/bcachefs/alloc_foreground.c:925
 open_bucket_add_buckets+0x347/0x580 fs/bcachefs/alloc_foreground.c:957
 bch2_alloc_sectors_start_trans+0x1de1/0x3560 fs/bcachefs/alloc_foreground.c:-1
 __bch2_btree_node_alloc fs/bcachefs/btree_update_interior.c:320 [inline]
 bch2_btree_reserve_get+0x9fd/0x2120 fs/bcachefs/btree_update_interior.c:534
 bch2_btree_update_start+0x2cf3/0x3620 fs/bcachefs/btree_update_interior.c:1289
 bch2_btree_node_rewrite+0x1cd/0x1b50 fs/bcachefs/btree_update_interior.c:2245
 bch2_btree_node_rewrite_key fs/bcachefs/btree_update_interior.c:2311 [inline]
 async_btree_node_rewrite_work+0x6e8/0x10d0 fs/bcachefs/btree_update_interior.c:2368
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xb91/0x1d80 kernel/workqueue.c:3321
 worker_thread+0xedf/0x1590 kernel/workqueue.c:3402
 kthread+0xd5c/0xf00 kernel/kthread.c:464
 ret_from_fork+0x1e0/0x310 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4154 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_noprof+0x95f/0x1310 mm/slub.c:4340
 kmalloc_noprof include/linux/slab.h:909 [inline]
 __bkey_cached_alloc fs/bcachefs/btree_key_cache.c:139 [inline]
 bkey_cached_alloc fs/bcachefs/btree_key_cache.c:162 [inline]
 btree_key_cache_create fs/bcachefs/btree_key_cache.c:231 [inline]
 btree_key_cache_fill+0x784/0x4780 fs/bcachefs/btree_key_cache.c:344
 bch2_btree_path_traverse_cached+0x10d7/0x1870 fs/bcachefs/btree_key_cache.c:399
 bch2_btree_path_traverse_one+0x6db/0x4060 fs/bcachefs/btree_iter.c:1179
 bch2_btree_path_traverse fs/bcachefs/btree_iter.h:250 [inline]
 bch2_btree_iter_peek_slot+0xd74/0x3910 fs/bcachefs/btree_iter.c:2781
 __bch2_bkey_get_iter fs/bcachefs/btree_iter.h:632 [inline]
 bch2_bkey_get_iter fs/bcachefs/btree_iter.h:646 [inline]
 bch2_check_discard_freespace_key+0x321/0x1a30 fs/bcachefs/alloc_background.c:1414
 try_alloc_bucket fs/bcachefs/alloc_foreground.c:272 [inline]
 bch2_bucket_alloc_freelist fs/bcachefs/alloc_foreground.c:420 [inline]
 bch2_bucket_alloc_trans+0x225d/0x3a40 fs/bcachefs/alloc_foreground.c:544
 bch2_bucket_alloc_set_trans+0xebb/0x1c10 fs/bcachefs/alloc_foreground.c:728
 __open_bucket_add_buckets+0x21f8/0x37b0 fs/bcachefs/alloc_foreground.c:925
 open_bucket_add_buckets+0x347/0x580 fs/bcachefs/alloc_foreground.c:957
 bch2_alloc_sectors_start_trans+0x1de1/0x3560 fs/bcachefs/alloc_foreground.c:-1
 __bch2_btree_node_alloc fs/bcachefs/btree_update_interior.c:320 [inline]
 bch2_btree_reserve_get+0x9fd/0x2120 fs/bcachefs/btree_update_interior.c:534
 bch2_btree_update_start+0x2cf3/0x3620 fs/bcachefs/btree_update_interior.c:1289
 bch2_btree_node_rewrite+0x1cd/0x1b50 fs/bcachefs/btree_update_interior.c:2245
 bch2_btree_node_rewrite_key fs/bcachefs/btree_update_interior.c:2311 [inline]
 async_btree_node_rewrite_work+0x6e8/0x10d0 fs/bcachefs/btree_update_interior.c:2368
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xb91/0x1d80 kernel/workqueue.c:3321
 worker_thread+0xedf/0x1590 kernel/workqueue.c:3402
 kthread+0xd5c/0xf00 kernel/kthread.c:464
 ret_from_fork+0x1e0/0x310 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

CPU: 1 UID: 0 PID: 4181 Comm: kworker/u8:21 Not tainted 6.16.0-rc2-syzkaller #0 PREEMPT(undef) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: btree_node_rewrite async_btree_node_rewrite_work
=====================================================


---
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