CVE-2025-38359

In the Linux kernel, the following vulnerability has been resolved:

s390/mm: Fix in_atomic() handling in do_secure_storage_access()

Kernel user spaces accesses to not exported pages in atomic context

incorrectly try to resolve the page fault.

With debug options enabled call traces like this can be seen:

BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1523

in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 419074, name: qemu-system-s39

preempt_count: 1, expected: 0

RCU nest depth: 0, expected: 0

INFO: lockdep is turned off.

Preemption disabled at:

[<00000383ea47cfa2>] copy_page_from_iter_atomic+0xa2/0x8a0

CPU: 12 UID: 0 PID: 419074 Comm: qemu-system-s39

Tainted: G W 6.16.0-20250531.rc0.git0.69b3a602feac.63.fc42.s390x+debug #1 PREEMPT

Tainted: [W]=WARN

Hardware name: IBM 3931 A01 703 (LPAR)

Call Trace:

[<00000383e990d282>] dump_stack_lvl+0xa2/0xe8

[<00000383e99bf152>] __might_resched+0x292/0x2d0

[<00000383eaa7c374>] down_read+0x34/0x2d0

[<00000383e99432f8>] do_secure_storage_access+0x108/0x360

[<00000383eaa724b0>] __do_pgm_check+0x130/0x220

[<00000383eaa842e4>] pgm_check_handler+0x114/0x160

[<00000383ea47d028>] copy_page_from_iter_atomic+0x128/0x8a0

([<00000383ea47d016>] copy_page_from_iter_atomic+0x116/0x8a0)

[<00000383e9c45eae>] generic_perform_write+0x16e/0x310

[<00000383e9eb87f4>] ext4_buffered_write_iter+0x84/0x160

[<00000383e9da0de4>] vfs_write+0x1c4/0x460

[<00000383e9da123c>] ksys_write+0x7c/0x100

[<00000383eaa7284e>] __do_syscall+0x15e/0x280

[<00000383eaa8417e>] system_call+0x6e/0x90

INFO: lockdep is turned off.

It is not allowed to take the mmap_lock while in atomic context. Therefore

handle such a secure storage access fault as if the accessed page is not

mapped: the uaccess function will return -EFAULT, and the caller has to

deal with this. Usually this means that the access is retried in process

context, which allows to resolve the page fault (or in this case export the

page).