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53f1d31708
H_PROTECT expects the flag value to include flags: AVPN, pp0, pp1, pp2, key0-key4, Noexec, CMO Option flags This patch updates hpte_updatepp() to fetch the storage key value from the linux page table and use the same in H_PROTECT hcall. native_hpte_updatepp() is not updated because the kernel doesn't clear the existing storage key value there. The kernel also doesn't use hpte_updatepp() callback for updating storage keys. This fixes the below kernel crash observed with KUAP enabled. BUG: Unable to handle kernel data access on write at 0xc009fffffc440000 Faulting instruction address: 0xc0000000000b7030 Key fault AMR: 0xfcffffffffffffff IAMR: 0xc0000077bc498100 Found HPTE: v = 0x40070adbb6fffc05 r = 0x1ffffffffff1194 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries ... CFAR: c000000000010100 DAR: c009fffffc440000 DSISR: 02200000 IRQMASK: 0 ... NIP memset+0x68/0x104 LR pcpu_alloc+0x54c/0xb50 Call Trace: pcpu_alloc+0x55c/0xb50 (unreliable) blk_stat_alloc_callback+0x94/0x150 blk_mq_init_allocated_queue+0x64/0x560 blk_mq_init_queue+0x54/0xb0 scsi_mq_alloc_queue+0x30/0xa0 scsi_alloc_sdev+0x1cc/0x300 scsi_probe_and_add_lun+0xb50/0x1020 __scsi_scan_target+0x17c/0x790 scsi_scan_channel+0x90/0xe0 scsi_scan_host_selected+0x148/0x1f0 do_scan_async+0x2c/0x2a0 async_run_entry_fn+0x78/0x220 process_one_work+0x264/0x540 worker_thread+0xa8/0x600 kthread+0x190/0x1a0 ret_from_kernel_thread+0x5c/0x6c With KUAP enabled the kernel uses storage key 3 for all its translations. But as shown by the debug print, in this specific case we have the hash page table entry created with key value 0. Found HPTE: v = 0x40070adbb6fffc05 r = 0x1ffffffffff1194 and DSISR indicates a key fault. This can happen due to parallel fault on the same EA by different CPUs: CPU 0 CPU 1 fault on X H_PAGE_BUSY set fault on X finish fault handling and clear H_PAGE_BUSY check for H_PAGE_BUSY continue with fault handling. This implies CPU1 will end up calling hpte_updatepp for address X and the kernel updated the hash pte entry with key 0 Fixes: d94b827e89dc ("powerpc/book3s64/kuap: Use Key 3 for kernel mapping with hash translation") Reported-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Debugged-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210326070755.304625-1-aneesh.kumar@linux.ibm.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.