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| author | Peter Xu <peterx@redhat.com> | 2021-05-14 17:27:04 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-05-19 10:08:29 +0200 |
| commit | f77aa56ad9894468a8eb43279d23c000aabb1cc5 (patch) | |
| tree | 377770d87b54b58d643d102072c50581bd8b7159 /mm | |
| parent | b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43 (diff) | |
| download | linux-stable-f77aa56ad9894468a8eb43279d23c000aabb1cc5.tar.gz linux-stable-f77aa56ad9894468a8eb43279d23c000aabb1cc5.tar.bz2 linux-stable-f77aa56ad9894468a8eb43279d23c000aabb1cc5.zip | |
mm/hugetlb: fix F_SEAL_FUTURE_WRITE
commit 22247efd822e6d263f3c8bd327f3f769aea9b1d9 upstream.
Patch series "mm/hugetlb: Fix issues on file sealing and fork", v2.
Hugh reported issue with F_SEAL_FUTURE_WRITE not applied correctly to
hugetlbfs, which I can easily verify using the memfd_test program, which
seems that the program is hardly run with hugetlbfs pages (as by default
shmem).
Meanwhile I found another probably even more severe issue on that hugetlb
fork won't wr-protect child cow pages, so child can potentially write to
parent private pages. Patch 2 addresses that.
After this series applied, "memfd_test hugetlbfs" should start to pass.
This patch (of 2):
F_SEAL_FUTURE_WRITE is missing for hugetlb starting from the first day.
There is a test program for that and it fails constantly.
$ ./memfd_test hugetlbfs
memfd-hugetlb: CREATE
memfd-hugetlb: BASIC
memfd-hugetlb: SEAL-WRITE
memfd-hugetlb: SEAL-FUTURE-WRITE
mmap() didn't fail as expected
Aborted (core dumped)
I think it's probably because no one is really running the hugetlbfs test.
Fix it by checking FUTURE_WRITE also in hugetlbfs_file_mmap() as what we
do in shmem_mmap(). Generalize a helper for that.
Link: https://lkml.kernel.org/r/20210503234356.9097-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20210503234356.9097-2-peterx@redhat.com
Fixes: ab3948f58ff84 ("mm/memfd: add an F_SEAL_FUTURE_WRITE seal to memfd")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/shmem.c | 22 |
1 files changed, 4 insertions, 18 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 662de44a9982..b119c44435bf 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2208,25 +2208,11 @@ out_nomem: static int shmem_mmap(struct file *file, struct vm_area_struct *vma) { struct shmem_inode_info *info = SHMEM_I(file_inode(file)); + int ret; - if (info->seals & F_SEAL_FUTURE_WRITE) { - /* - * New PROT_WRITE and MAP_SHARED mmaps are not allowed when - * "future write" seal active. - */ - if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_WRITE)) - return -EPERM; - - /* - * Since an F_SEAL_FUTURE_WRITE sealed memfd can be mapped as - * MAP_SHARED and read-only, take care to not allow mprotect to - * revert protections on such mappings. Do this only for shared - * mappings. For private mappings, don't need to mask - * VM_MAYWRITE as we still want them to be COW-writable. - */ - if (vma->vm_flags & VM_SHARED) - vma->vm_flags &= ~(VM_MAYWRITE); - } + ret = seal_check_future_write(info->seals, vma); + if (ret) + return ret; file_accessed(file); vma->vm_ops = &shmem_vm_ops; |