From: Andrew Morton <akpm@linux-foundation.org>
To: aarcange@redhat.com, akpm@linux-foundation.org,
linux-mm@kvack.org, liwang@redhat.com,
mm-commits@vger.kernel.org, namit@vmware.com, peterx@redhat.com,
stable@vger.kernel.org, torvalds@linux-foundation.org
Subject: [patch 02/19] userfaultfd: fix a race between writeprotect and exit_mmap()
Date: Mon, 18 Oct 2021 15:15:25 -0700 [thread overview]
Message-ID: <20211018221525.vqm6hS1Ya%akpm@linux-foundation.org> (raw)
In-Reply-To: <20211018151438.f2246e2656c041b6753a8bdd@linux-foundation.org>
From: Nadav Amit <namit@vmware.com>
Subject: userfaultfd: fix a race between writeprotect and exit_mmap()
A race is possible when a process exits, its VMAs are removed by
exit_mmap() and at the same time userfaultfd_writeprotect() is called.
The race was detected by KASAN on a development kernel, but it appears to
be possible on vanilla kernels as well.
Use mmget_not_zero() to prevent the race as done in other userfaultfd
operations.
Link: https://lkml.kernel.org/r/20210921200247.25749-1-namit@vmware.com
Fixes: 63b2d4174c4ad ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl")
Signed-off-by: Nadav Amit <namit@vmware.com>
Tested-by: Li Wang <liwang@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
fs/userfaultfd.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
--- a/fs/userfaultfd.c~userfaultfd-fix-a-race-between-writeprotect-and-exit_mmap
+++ a/fs/userfaultfd.c
@@ -1827,9 +1827,15 @@ static int userfaultfd_writeprotect(stru
if (mode_wp && mode_dontwake)
return -EINVAL;
- ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start,
- uffdio_wp.range.len, mode_wp,
- &ctx->mmap_changing);
+ if (mmget_not_zero(ctx->mm)) {
+ ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start,
+ uffdio_wp.range.len, mode_wp,
+ &ctx->mmap_changing);
+ mmput(ctx->mm);
+ } else {
+ return -ESRCH;
+ }
+
if (ret)
return ret;
_
next prev parent reply other threads:[~2021-10-18 22:15 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-18 22:14 incoming Andrew Morton
2021-10-18 22:15 ` [patch 01/19] mm/userfaultfd: selftests: fix memory corruption with thp enabled Andrew Morton
2021-10-18 22:15 ` Andrew Morton [this message]
2021-10-18 22:15 ` [patch 03/19] mm/migrate: optimize hotplug-time demotion order updates Andrew Morton
2021-10-18 22:15 ` [patch 04/19] mm/migrate: add CPU hotplug to demotion #ifdef Andrew Morton
2021-10-18 22:15 ` [patch 05/19] mm/migrate: fix CPUHP state to update node demotion order Andrew Morton
2021-10-18 22:15 ` [patch 06/19] ocfs2: fix data corruption after conversion from inline format Andrew Morton
2021-10-18 22:15 ` [patch 07/19] ocfs2: mount fails with buffer overflow in strlen Andrew Morton
2021-10-18 22:15 ` [patch 08/19] memblock: check memory total_size Andrew Morton
2021-10-18 22:15 ` [patch 09/19] mm/mempolicy: do not allow illegal MPOL_F_NUMA_BALANCING | MPOL_LOCAL in mbind() Andrew Morton
2021-10-18 22:15 ` [patch 10/19] mm, slub: fix two bugs in slab_debug_trace_open() Andrew Morton
2021-10-18 22:15 ` [patch 11/19] mm, slub: fix mismatch between reconstructed freelist depth and cnt Andrew Morton
2021-10-18 22:15 ` [patch 12/19] mm, slub: fix potential memoryleak in kmem_cache_open() Andrew Morton
2021-10-18 22:16 ` [patch 13/19] mm, slub: fix potential use-after-free in slab_debugfs_fops Andrew Morton
2021-10-18 22:16 ` [patch 14/19] mm, slub: fix incorrect memcg slab count for bulk free Andrew Morton
2021-10-18 22:16 ` [patch 15/19] elfcore: correct reference to CONFIG_UML Andrew Morton
2021-10-18 22:16 ` [patch 16/19] vfs: check fd has read access in kernel_read_file_from_fd() Andrew Morton
2021-10-18 22:16 ` [patch 17/19] mm/secretmem: fix NULL page->mapping dereference in page_is_secretmem() Andrew Morton
2021-10-18 22:16 ` [patch 18/19] mm/thp: decrease nr_thps in file's mapping on THP split Andrew Morton
2021-10-18 22:16 ` [patch 19/19] mailmap: add Andrej Shadura Andrew Morton
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