From: Lokesh Gidra <lokeshgidra@google.com>
To: akpm@linux-foundation.org
Cc: lokeshgidra@google.com, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
selinux@vger.kernel.org, surenb@google.com,
kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com,
david@redhat.com, axelrasmussen@google.com, bgeffon@google.com,
willy@infradead.org, jannh@google.com, kaleshsingh@google.com,
ngeoffray@google.com
Subject: [PATCH] userfaultfd: fix mmap_changing checking in mfill_atomic_hugetlb
Date: Wed, 17 Jan 2024 14:37:29 -0800 [thread overview]
Message-ID: <20240117223729.1444522-1-lokeshgidra@google.com> (raw)
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().
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
---
mm/userfaultfd.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 20e3b0d9cf7e..75fcf1f783bc 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -357,6 +357,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
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 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
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(struct vm_area_struct *dst_vma,
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 @@ static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm,
* 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;
--
2.43.0.429.g432eaa2c6b-goog
next reply other threads:[~2024-01-17 22:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-17 22:37 Lokesh Gidra [this message]
2024-01-18 21:59 ` [PATCH] userfaultfd: fix mmap_changing checking in mfill_atomic_hugetlb Andrew Morton
2024-01-18 23:29 ` Axel Rasmussen
[not found] ` <CAJHvVcgTk3Cf2i-ONx=jH_-dz9GktVMv1Sdqv3cCk6nP2k++iA@mail.gmail.com>
2024-01-25 9:36 ` Mike Rapoport
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