[syzbot] [bcachefs?] KMSAN: uninit-value in bch2_readdir (2)

[syzbot] [bcachefs?] KMSAN: uninit-value in bch2_readdir (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    fbfd64d25c7a Merge tag 'vfs-6.13-rc7.fixes' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=125755c4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=93fafdd434f3247d
dashboard link: https://syzkaller.appspot.com/bug?extid=a7b475122da841580575
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/be5f7d21fc6d/disk-fbfd64d2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/18656986c542/vmlinux-fbfd64d2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/23240d42568c/bzImage-fbfd64d2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a7b475122da841580575@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in bch2_dirent_read_target fs/bcachefs/dirent.c:259 [inline]
BUG: KMSAN: uninit-value in bch2_readdir+0x1a45/0x2470 fs/bcachefs/dirent.c:551
 bch2_dirent_read_target fs/bcachefs/dirent.c:259 [inline]
 bch2_readdir+0x1a45/0x2470 fs/bcachefs/dirent.c:551
 bch2_vfs_readdir+0x347/0x7c0 fs/bcachefs/fs.c:1377
 iterate_dir+0x5b3/0x9e0 fs/readdir.c:108
 __do_sys_getdents fs/readdir.c:322 [inline]
 __se_sys_getdents+0x170/0x550 fs/readdir.c:308
 __x64_sys_getdents+0x96/0xe0 fs/readdir.c:308
 x64_sys_call+0x38d8/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:79
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was stored to memory at:
 memcpy_u64s_small fs/bcachefs/util.h:393 [inline]
 bkey_reassemble fs/bcachefs/bkey.h:513 [inline]
 bch2_bkey_buf_reassemble fs/bcachefs/bkey_buf.h:28 [inline]
 bch2_readdir+0x14f7/0x2470 fs/bcachefs/dirent.c:551
 bch2_vfs_readdir+0x347/0x7c0 fs/bcachefs/fs.c:1377
 iterate_dir+0x5b3/0x9e0 fs/readdir.c:108
 __do_sys_getdents fs/readdir.c:322 [inline]
 __se_sys_getdents+0x170/0x550 fs/readdir.c:308
 __x64_sys_getdents+0x96/0xe0 fs/readdir.c:308
 x64_sys_call+0x38d8/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:79
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 ___kmalloc_large_node+0x22c/0x370 mm/slub.c:4253
 __kmalloc_large_node_noprof+0x3f/0x1e0 mm/slub.c:4270
 __do_kmalloc_node mm/slub.c:4286 [inline]
 __kmalloc_node_noprof+0xc96/0x1250 mm/slub.c:4304
 __kvmalloc_node_noprof+0xc0/0x2d0 mm/util.c:645
 btree_bounce_alloc fs/bcachefs/btree_io.c:124 [inline]
 btree_node_sort+0x78a/0x1d30 fs/bcachefs/btree_io.c:323
 bch2_btree_post_write_cleanup+0x1b0/0xf20 fs/bcachefs/btree_io.c:2248
 bch2_btree_node_write+0x21c/0x2e0 fs/bcachefs/btree_io.c:2289
 btree_node_write_if_need fs/bcachefs/btree_io.h:151 [inline]
 __btree_node_flush+0x606/0x680 fs/bcachefs/btree_trans_commit.c:252
 bch2_btree_node_flush0+0x35/0x60 fs/bcachefs/btree_trans_commit.c:261
 journal_flush_pins+0xce6/0x1780 fs/bcachefs/journal_reclaim.c:565
 __bch2_journal_reclaim+0xda8/0x1670 fs/bcachefs/journal_reclaim.c:698
 bch2_journal_reclaim_thread+0x18e/0x760 fs/bcachefs/journal_reclaim.c:740
 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

CPU: 0 UID: 0 PID: 9169 Comm: syz.7.774 Not tainted 6.13.0-rc6-syzkaller-00036-gfbfd64d25c7a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
=====================================================


---
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***

Subject: 
Author: kent.overstreet@linux.dev

#syz fix bcachefs: Disable asm memcpys when kmsan enabled