diff options
author | Ralph Campbell <rcampbell@nvidia.com> | 2018-10-30 15:04:14 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-10-31 08:54:11 -0700 |
commit | 86a2d59841ab0b147ffc1b7b3041af87927cf312 (patch) | |
tree | d10b1917669b769bfa3192228b05feec7f473e5f /mm/hmm.c | |
parent | aab8d0520e6e7c2a61f71195e6ce7007a4843afb (diff) | |
download | linux-stable-86a2d59841ab0b147ffc1b7b3041af87927cf312.tar.gz linux-stable-86a2d59841ab0b147ffc1b7b3041af87927cf312.tar.bz2 linux-stable-86a2d59841ab0b147ffc1b7b3041af87927cf312.zip |
mm/hmm: fix race between hmm_mirror_unregister() and mmu_notifier callback
In hmm_mirror_unregister(), mm->hmm is set to NULL and then
mmu_notifier_unregister_no_release() is called. That creates a small
window where mmu_notifier can call mmu_notifier_ops with mm->hmm equal to
NULL. Fix this by first unregistering mmu notifier callbacks and then
setting mm->hmm to NULL.
Similarly in hmm_register(), set mm->hmm before registering mmu_notifier
callbacks so callback functions always see mm->hmm set.
Link: http://lkml.kernel.org/r/20181019160442.18723-4-jglisse@redhat.com
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/hmm.c')
-rw-r--r-- | mm/hmm.c | 36 |
1 files changed, 21 insertions, 15 deletions
@@ -91,16 +91,6 @@ static struct hmm *hmm_register(struct mm_struct *mm) spin_lock_init(&hmm->lock); hmm->mm = mm; - /* - * We should only get here if hold the mmap_sem in write mode ie on - * registration of first mirror through hmm_mirror_register() - */ - hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops; - if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) { - kfree(hmm); - return NULL; - } - spin_lock(&mm->page_table_lock); if (!mm->hmm) mm->hmm = hmm; @@ -108,12 +98,27 @@ static struct hmm *hmm_register(struct mm_struct *mm) cleanup = true; spin_unlock(&mm->page_table_lock); - if (cleanup) { - mmu_notifier_unregister(&hmm->mmu_notifier, mm); - kfree(hmm); - } + if (cleanup) + goto error; + + /* + * We should only get here if hold the mmap_sem in write mode ie on + * registration of first mirror through hmm_mirror_register() + */ + hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops; + if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) + goto error_mm; return mm->hmm; + +error_mm: + spin_lock(&mm->page_table_lock); + if (mm->hmm == hmm) + mm->hmm = NULL; + spin_unlock(&mm->page_table_lock); +error: + kfree(hmm); + return NULL; } void hmm_mm_destroy(struct mm_struct *mm) @@ -278,12 +283,13 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror) if (!should_unregister || mm == NULL) return; + mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm); + spin_lock(&mm->page_table_lock); if (mm->hmm == hmm) mm->hmm = NULL; spin_unlock(&mm->page_table_lock); - mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm); kfree(hmm); } EXPORT_SYMBOL(hmm_mirror_unregister); |