From: Dave Chinner dchinner@redhat.com
commit 0573676fdde7ce3829ee6a42a8e5a56355234712 upstream.
Alexander Potapenko report that KMSAN was issuing these warnings:
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
This is caused by the struct xfs_log_dinode not having the di_crc field initialised. Log recovery never uses this field (it is only present these days for on-disk format compatibility reasons) and so it's value is never checked so nothing in XFS has caught this.
Further, none of the uninitialised memory access warning tools have caught this (despite catching other uninit memory accesses in the struct xfs_log_dinode back in 2017!) until recently. Alexander annotated the XFS code to get the dump of the actual bytes that were detected as uninitialised, and from that report it took me about 30s to realise what the issue was.
The issue was introduced back in 2016 and every inode that is logged fails to initialise this field. This is no actual bad behaviour caused by this issue - I find it hard to even classify it as a bug...
Reported-and-tested-by: Alexander Potapenko glider@google.com Fixes: f8d55aa0523a ("xfs: introduce inode log format object") Signed-off-by: Dave Chinner dchinner@redhat.com Reviewed-by: "Darrick J. Wong" djwong@kernel.org Signed-off-by: Chandan Babu R chandanbabu@kernel.org Signed-off-by: Catherine Hoang catherine.hoang@oracle.com Acked-by: Darrick J. Wong djwong@kernel.org --- fs/xfs/xfs_inode_item.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c index 127b2410eb20..155a8b312875 100644 --- a/fs/xfs/xfs_inode_item.c +++ b/fs/xfs/xfs_inode_item.c @@ -556,6 +556,9 @@ xfs_inode_to_log_dinode( memset(to->di_pad2, 0, sizeof(to->di_pad2)); uuid_copy(&to->di_uuid, &ip->i_mount->m_sb.sb_meta_uuid); to->di_v3_pad = 0; + + /* dummy value for initialisation */ + to->di_crc = 0; } else { to->di_version = 2; to->di_flushiter = ip->i_flushiter;