The patch titled
Subject: userfaultfd: fix mmap_changing checking in mfill_atomic_hugetlb
has been added to the -mm mm-unstable branch. Its filename is
userfaultfd-fix-mmap_changing-checking-in-mfill_atomic_hugetlb.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/userfaultfd-fix-mmap_changing-checking-in-mfill_atomic_hugetlb.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Lokesh Gidra <lokeshgidra@xxxxxxxxxx>
Subject: userfaultfd: fix mmap_changing checking in mfill_atomic_hugetlb
Date: Wed, 17 Jan 2024 14:37:29 -0800
In mfill_atomic_hugetlb(), mmap_changing isn't being checked
again if we drop mmap_lock and reacquire it. When the lock is not held,
mmap_changing could have been incremented. This is also inconsistent
with the behavior in mfill_atomic().
Link: https://lkml.kernel.org/r/20240117223729.1444522-1-lokeshgidra@xxxxxxxxxx
Signed-off-by: Lokesh Gidra <lokeshgidra@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: Brian Geffon <bgeffon@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Nicolas Geoffray <ngeoffray@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/userfaultfd.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
--- a/mm/userfaultfd.c~userfaultfd-fix-mmap_changing-checking-in-mfill_atomic_hugetlb
+++ a/mm/userfaultfd.c
@@ -357,6 +357,7 @@ static __always_inline ssize_t mfill_ato
unsigned long dst_start,
unsigned long src_start,
unsigned long len,
+ atomic_t *mmap_changing,
uffd_flags_t flags)
{
struct mm_struct *dst_mm = dst_vma->vm_mm;
@@ -472,6 +473,15 @@ retry:
goto out;
}
mmap_read_lock(dst_mm);
+ /*
+ * If memory mappings are changing because of non-cooperative
+ * operation (e.g. mremap) running in parallel, bail out and
+ * request the user to retry later
+ */
+ if (mmap_changing && atomic_read(mmap_changing)) {
+ err = -EAGAIN;
+ break;
+ }
dst_vma = NULL;
goto retry;
@@ -506,6 +516,7 @@ extern ssize_t mfill_atomic_hugetlb(stru
unsigned long dst_start,
unsigned long src_start,
unsigned long len,
+ atomic_t *mmap_changing,
uffd_flags_t flags);
#endif /* CONFIG_HUGETLB_PAGE */
@@ -622,8 +633,8 @@ retry:
* If this is a HUGETLB vma, pass off to appropriate routine
*/
if (is_vm_hugetlb_page(dst_vma))
- return mfill_atomic_hugetlb(dst_vma, dst_start,
- src_start, len, flags);
+ return mfill_atomic_hugetlb(dst_vma, dst_start, src_start,
+ len, mmap_changing, flags);
if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
goto out_unlock;
_
Patches currently in -mm which might be from lokeshgidra@xxxxxxxxxx are
userfaultfd-fix-return-error-if-mmap_changing-is-non-zero-in-move-ioctl.patch
userfaultfd-fix-mmap_changing-checking-in-mfill_atomic_hugetlb.patch
