6.15-stable review patch. If anyone has any objections, please let me know.
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From: Heiko Carstens hca@linux.ibm.com
[ Upstream commit 11709abccf93b08adde95ef313c300b0d4bc28f1 ]
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).
Reviewed-by: Claudio Imbrenda imbrenda@linux.ibm.com Acked-by: Alexander Gordeev agordeev@linux.ibm.com Acked-by: Christian Borntraeger borntraeger@linux.ibm.com Link: https://lore.kernel.org/r/20250603134936.1314139-1-hca@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/mm/fault.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c index da84ff6770dec..8b3f6dd00eab2 100644 --- a/arch/s390/mm/fault.c +++ b/arch/s390/mm/fault.c @@ -442,6 +442,8 @@ void do_secure_storage_access(struct pt_regs *regs) if (rc) BUG(); } else { + if (faulthandler_disabled()) + return handle_fault_error_nolock(regs, 0); mm = current->mm; mmap_read_lock(mm); vma = find_vma(mm, addr);