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| author | David Hildenbrand <david@redhat.com> | 2024-09-26 17:42:34 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-10-09 21:47:19 +0200 |
| commit | 47fa30118f02dc50e1c57242c6b72542c871b178 (patch) | |
| tree | e2ad21ea7396c4b0ad95cc718b329d1fe1fa1843 /mm/huge_memory.c | |
| parent | resource, kunit: fix user-after-free in resource_test_region_intersects() (diff) | |
| download | linux-47fa30118f02dc50e1c57242c6b72542c871b178.tar.xz linux-47fa30118f02dc50e1c57242c6b72542c871b178.zip | |
mm/huge_memory: check pmd_special() only after pmd_present()
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>
Diffstat (limited to 'mm/huge_memory.c')
| -rw-r--r-- | mm/huge_memory.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 3ca89e0279a7..87b49ecc7b1e 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1586,7 +1586,7 @@ 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); |