From: Oleg Nesterov <oleg@redhat.com>
To: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: linux-mm <linux-mm@kvack.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Peter Xu <peterx@redhat.com>, Mike Rapoport <rppt@linux.ibm.com>,
Jann Horn <jannh@google.com>, Jason Gunthorpe <jgg@mellanox.com>,
Michal Hocko <mhocko@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
linux-kernel@vger.kernel.org
Subject: [PATCH] userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx
Date: Tue, 20 Aug 2019 18:02:38 +0200 [thread overview]
Message-ID: <20190820160237.GB4983@redhat.com> (raw)
In-Reply-To: <d4583416-5e4a-95e7-a08a-32bf2c9a95fb@huawei.com>
userfaultfd_release() should clear vm_flags/vm_userfaultfd_ctx even
if mm->core_state != NULL.
Otherwise a page fault can see userfaultfd_missing() == T and use an
already freed userfaultfd_ctx.
Reported-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Fixes: 04f5866e41fb ("coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping")
Cc: stable@vger.kernel.org
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
fs/userfaultfd.c | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index ccbdbd6..fe6d804 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -880,6 +880,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
/* len == 0 means wake all */
struct userfaultfd_wake_range range = { .len = 0, };
unsigned long new_flags;
+ bool still_valid;
WRITE_ONCE(ctx->released, true);
@@ -895,8 +896,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
* taking the mmap_sem for writing.
*/
down_write(&mm->mmap_sem);
- if (!mmget_still_valid(mm))
- goto skip_mm;
+ still_valid = mmget_still_valid(mm);
prev = NULL;
for (vma = mm->mmap; vma; vma = vma->vm_next) {
cond_resched();
@@ -907,19 +907,20 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
continue;
}
new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
- prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end,
- new_flags, vma->anon_vma,
- vma->vm_file, vma->vm_pgoff,
- vma_policy(vma),
- NULL_VM_UFFD_CTX);
- if (prev)
- vma = prev;
- else
- prev = vma;
+ if (still_valid) {
+ prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end,
+ new_flags, vma->anon_vma,
+ vma->vm_file, vma->vm_pgoff,
+ vma_policy(vma),
+ NULL_VM_UFFD_CTX);
+ if (prev)
+ vma = prev;
+ else
+ prev = vma;
+ }
vma->vm_flags = new_flags;
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
}
-skip_mm:
up_write(&mm->mmap_sem);
mmput(mm);
wakeup:
--
2.5.0
next prev parent reply other threads:[~2019-08-20 16:02 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-13 9:08 [BUG] kernel BUG at fs/userfaultfd.c:385 after 04f5866e41fb Kefeng Wang
2019-08-14 13:53 ` Michal Hocko
2019-08-14 14:45 ` Kefeng Wang
2019-08-14 15:10 ` Oleg Nesterov
2019-08-14 15:41 ` Oleg Nesterov
2019-08-15 2:21 ` Kefeng Wang
2019-08-15 9:54 ` Oleg Nesterov
2019-08-16 10:37 ` Kefeng Wang
2019-08-19 12:48 ` Oleg Nesterov
2019-08-19 16:05 ` Andrea Arcangeli
2019-08-20 15:59 ` Oleg Nesterov
2019-08-20 16:15 ` Andrea Arcangeli
[not found] ` <73d7b5b1-a88c-5fca-ba16-be214c2524a4@I-love.SAKURA.ne.jp>
2019-08-20 16:09 ` Oleg Nesterov
2019-08-20 16:02 ` Oleg Nesterov [this message]
2019-08-20 16:05 ` [PATCH] userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx Andrea Arcangeli
2019-08-21 0:53 ` Kefeng Wang
2019-08-27 16:33 ` [BUG] kernel BUG at fs/userfaultfd.c:385 after 04f5866e41fb Oleg Nesterov
2019-08-27 17:14 ` Andrea Arcangeli
2019-08-28 14:25 ` Oleg Nesterov
2019-08-29 12:05 ` Andrea Arcangeli
2019-08-30 16:49 ` Oleg Nesterov
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