CVE-2024-27031: In the Linux kernel, the following vulnerability has been resolved:  NFS: Fix nfs_netfs_issue_read() xarray locking for writeback interrupt  The loop inside nfs_netfs_issue_read() currently does not disable interrupts while iterating through pages in the xarray to submit for NFS read.  This is not safe though since after taking xa_lock, another page in the mapping could be processed for writeback inside an interrupt, and deadlock can occur.  The fix is simple and clean if we use xa_for_each_range(), which handles the iteration with RCU while reducing code complexity.  The problem is easily reproduced with the following test:  mount -o vers=3,fsc 127.0.0.1:/export /mnt/nfs  dd if=/dev/zero of=/mnt/nfs/file1.bin bs=4096 count=1  echo 3 > /proc/sys/vm/drop_caches  dd if=/mnt/nfs/file1.bin of=/dev/null  umount /mnt/nfs  On the console with a lockdep-enabled kernel a message similar to the following will be seen:   ================================  WARNING: inconsistent lock state  6.7.0-lockdbg+ #10 Not tainted  --------------------------------  inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.  test5/1708 [HC0[0]:SC0[0]:HE1:SE1] takes:  ffff888127baa598 (&xa->xa_lock#4){+.?.}-{3:3}, at: nfs_netfs_issue_read+0x1b2/0x4b0 [nfs]  {IN-SOFTIRQ-W} state was registered at:    lock_acquire+0x144/0x380    _raw_spin_lock_irqsave+0x4e/0xa0    __folio_end_writeback+0x17e/0x5c0    folio_end_writeback+0x93/0x1b0    iomap_finish_ioend+0xeb/0x6a0    blk_update_request+0x204/0x7f0    blk_mq_end_request+0x30/0x1c0    blk_complete_reqs+0x7e/0xa0    __do_softirq+0x113/0x544    __irq_exit_rcu+0xfe/0x120    irq_exit_rcu+0xe/0x20    sysvec_call_function_single+0x6f/0x90    asm_sysvec_call_function_single+0x1a/0x20    pv_native_safe_halt+0xf/0x20    default_idle+0x9/0x20    default_idle_call+0x67/0xa0    do_idle+0x2b5/0x300    cpu_startup_entry+0x34/0x40    start_secondary+0x19d/0x1c0    secondary_startup_64_no_verify+0x18f/0x19b  irq event stamp: 176891  hardirqs last  enabled at (176891): [<ffffffffa67a0be4>] _raw_spin_unlock_irqrestore+0x44/0x60  hardirqs last disabled at (176890): [<ffffffffa67a0899>] _raw_spin_lock_irqsave+0x79/0xa0  softirqs last  enabled at (176646): [<ffffffffa515d91e>] __irq_exit_rcu+0xfe/0x120  softirqs last disabled at (176633): [<ffffffffa515d91e>] __irq_exit_rcu+0xfe/0x120   other info that might help us debug this:   Possible unsafe locking scenario:          CPU0         ----    lock(&xa->xa_lock#4);    <Interrupt>      lock(&xa->xa_lock#4);    *** DEADLOCK ***   2 locks held by test5/1708:   #0: ffff888127baa498 (&sb->s_type->i_mutex_key#22){++++}-{4:4}, at:       nfs_start_io_read+0x28/0x90 [nfs]   #1: ffff888127baa650 (mapping.invalidate_lock#3){.+.+}-{4:4}, at:       page_cache_ra_unbounded+0xa4/0x280   stack backtrace:  CPU: 6 PID: 1708 Comm: test5 Kdump: loaded Not tainted 6.7.0-lockdbg+  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-1.fc39 04/01/2014  Call Trace:   dump_stack_lvl+0x5b/0x90   mark_lock+0xb3f/0xd20   __lock_acquire+0x77b/0x3360   _raw_spin_lock+0x34/0x80   nfs_netfs_issue_read+0x1b2/0x4b0 [nfs]   netfs_begin_read+0x77f/0x980 [netfs]   nfs_netfs_readahead+0x45/0x60 [nfs]   nfs_readahead+0x323/0x5a0 [nfs]   read_pages+0xf3/0x5c0   page_cache_ra_unbounded+0x1c8/0x280   filemap_get_pages+0x38c/0xae0   filemap_read+0x206/0x5e0   nfs_file_read+0xb7/0x140 [nfs]   vfs_read+0x2a9/0x460   ksys_read+0xb7/0x140