On 5/26/21 4:57 PM, Anatoly Pugachev wrote:
On Tue, May 25, 2021 at 4:03 PM Gerald Schaefer gerald.schaefer@linux.ibm.com wrote:
In pmd/pud_advanced_tests(), the vaddr is aligned up to the next pmd/pud entry, and so it does not match the given pmdp/pudp and (aligned down) pfn any more.
For s390, this results in memory corruption, because the IDTE instruction used e.g. in xxx_get_and_clear() will take the vaddr for some calculations, in combination with the given pmdp. It will then end up with a wrong table origin, ending on ...ff8, and some of those wrongly set low-order bits will also select a wrong pagetable level for the index addition. IDTE could therefore invalidate (or 0x20) something outside of the page tables, depending on the wrongly picked index, which in turn depends on the random vaddr.
As result, we sometimes see "BUG task_struct (Not tainted): Padding overwritten" on s390, where one 0x5a padding value got overwritten with 0x7a.
Fix this by aligning down, similar to how the pmd/pud_aligned pfns are calculated.
Fixes: a5c3b9ffb0f40 ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers") Cc: stable@vger.kernel.org # v5.9+ Signed-off-by: Gerald Schaefer gerald.schaefer@linux.ibm.com
boot tested on sparc64 with quick run of stress-ng ( --class memory --sequential -1 --timeout 10s -v --pathological --oomable --metrics-brief ) stress-ng: debug: [371408] system: Linux ttip 5.13.0-rc3-00043-gad9f25d33860-dirty #218 SMP Wed May 26 11:55:54 MSK 2021 sparc64
Tested-by: Anatoly Pugachev matorola@gmail.com
spac64 does not enable ARCH_HAS_DEBUG_VM_PGTABLE, did you enable it before running the test ? Did the entire test debug_vm_pgtable() run successfully on sparc64 ?