From: David Hildenbrand <david@redhat.com> mainline inclusion from mainline-v6.12-rc1 commit 47fa30118f02dc50e1c57242c6b72542c871b178 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ID4NL4 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- We should only check for pmd_special() after we made sure that we have a present PMD. For example, if we have a migration PMD, pmd_special() might indicate that we have a special PMD although we really don't. This fixes confusing migration entries as PFN mappings, and not doing what we are supposed to do in the "is_swap_pmd()" case further down in the function -- including messing up COW, page table handling and accounting. Link: https://lkml.kernel.org/r/20240926154234.2247217-1-david@redhat.com Fixes: bc02afbd4d73 ("mm/fork: accept huge pfnmap entries") Signed-off-by: David Hildenbrand <david@redhat.com> Reported-by: syzbot+bf2c35fa302ebe3c7471@syzkaller.appspotmail.com Closes: https://lore.kernel.org/lkml/66f15c8d.050a0220.c23dd.000f.GAE@google.com/ Reviewed-by: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Yin Tirui <yintirui@huawei.com> --- mm/huge_memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 345636830b74..b9eb0f2f5c90 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1807,7 +1807,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, int ret = -ENOMEM; pmd = pmdp_get_lockless(src_pmd); - if (unlikely(pmd_special(pmd))) { + if (unlikely(pmd_present(pmd) && pmd_special(pmd))) { dst_ptl = pmd_lock(dst_mm, dst_pmd); src_ptl = pmd_lockptr(src_mm, src_pmd); spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); -- 2.43.0