linux-kernel - [syzbot] [crypto?] KMSAN: uninit-value in __crc32c_le

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Date:   Wed, 13 Dec 2023 11:49:50 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     syzbot+a6d6b8fffa294705dbd8@...kaller.appspotmail.com, hch@....de,
        dchinner@...hat.com
Cc:     davem@...emloft.net, glider@...gle.com,
        herbert@...dor.apana.org.au, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [crypto?] KMSAN: uninit-value in __crc32c_le_base (3)

Hi Christoph, Dave,

The repro provided by Xingwei indeed works.

I tried adding kmsan_check_memory(data, write_len) to xlog_write_iovec(), and
it reported an uninitialized hole inside the `data` buffer:

kmalloc-ed xlog buffer of size 512 : ffff88802fc26200
kmalloc-ed xlog buffer of size 368 : ffff88802fc24a00
kmalloc-ed xlog buffer of size 648 : ffff88802b631000
kmalloc-ed xlog buffer of size 648 : ffff88802b632800
kmalloc-ed xlog buffer of size 648 : ffff88802b631c00
xlog_write_iovec: copying 12 bytes from ffff888017ddbbd8 to ffff88802c300400
xlog_write_iovec: copying 28 bytes from ffff888017ddbbe4 to ffff88802c30040c
xlog_write_iovec: copying 68 bytes from ffff88802fc26274 to ffff88802c300428
xlog_write_iovec: copying 188 bytes from ffff88802fc262bc to ffff88802c30046c
=====================================================
BUG: KMSAN: uninit-value in xlog_write_iovec fs/xfs/xfs_log.c:2227
BUG: KMSAN: uninit-value in xlog_write_full fs/xfs/xfs_log.c:2263
BUG: KMSAN: uninit-value in xlog_write+0x1fac/0x2600 fs/xfs/xfs_log.c:2532
 xlog_write_iovec fs/xfs/xfs_log.c:2227
 xlog_write_full fs/xfs/xfs_log.c:2263
 xlog_write+0x1fac/0x2600 fs/xfs/xfs_log.c:2532
 xlog_cil_write_chain fs/xfs/xfs_log_cil.c:918
 xlog_cil_push_work+0x30f2/0x44e0 fs/xfs/xfs_log_cil.c:1263
 process_one_work kernel/workqueue.c:2630
 process_scheduled_works+0x1188/0x1e30 kernel/workqueue.c:2703
 worker_thread+0xee5/0x14f0 kernel/workqueue.c:2784
 kthread+0x391/0x500 kernel/kthread.c:388
 ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

Uninit was created at:
 slab_post_alloc_hook+0x101/0xac0 mm/slab.h:768
 slab_alloc_node mm/slub.c:3482
 __kmem_cache_alloc_node+0x612/0xae0 mm/slub.c:3521
 __do_kmalloc_node mm/slab_common.c:1006
 __kmalloc+0x11a/0x410 mm/slab_common.c:1020
 kmalloc ./include/linux/slab.h:604
 xlog_kvmalloc fs/xfs/xfs_log_priv.h:704
 xlog_cil_alloc_shadow_bufs fs/xfs/xfs_log_cil.c:343
 xlog_cil_commit+0x487/0x4dc0 fs/xfs/xfs_log_cil.c:1574
 __xfs_trans_commit+0x8df/0x1930 fs/xfs/xfs_trans.c:1017
 xfs_trans_commit+0x30/0x40 fs/xfs/xfs_trans.c:1061
 xfs_create+0x15af/0x2150 fs/xfs/xfs_inode.c:1076
 xfs_generic_create+0x4cd/0x1550 fs/xfs/xfs_iops.c:199
 xfs_vn_create+0x4a/0x60 fs/xfs/xfs_iops.c:275
 lookup_open fs/namei.c:3477
 open_last_lookups fs/namei.c:3546
 path_openat+0x29ac/0x6180 fs/namei.c:3776
 do_filp_open+0x24d/0x680 fs/namei.c:3809
 do_sys_openat2+0x1bc/0x330 fs/open.c:1440
 do_sys_open fs/open.c:1455
 __do_sys_openat fs/open.c:1471
 __se_sys_openat fs/open.c:1466
 __x64_sys_openat+0x253/0x330 fs/open.c:1466
 do_syscall_x64 arch/x86/entry/common.c:51
 do_syscall_64+0x4f/0x140 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b arch/x86/entry/entry_64.S:120

Bytes 112-115 of 188 are uninitialized
Memory access of size 188 starts at ffff88802fc262bc

CPU: 1 PID: 1061 Comm: kworker/u9:6 Tainted: G    B              6.7.0-rc3-gcaca734ed6a9-dirty #112
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
Workqueue: xfs-cil/loop0 xlog_cil_push_work
=====================================================

Do you know if this is expected?