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authorPeter Xu <peterx@redhat.com>2023-04-12 12:38:52 -0400
committerAndrew Morton <akpm@linux-foundation.org>2023-04-16 10:41:26 -0700
commit2ff559f31a5d50c31a3f9d849f8af90dc36c7105 (patch)
tree40ece38e4052a27e22948a6dd6c15c696afe38af
parent1ba1199ec5747f475538c0d25a32804e5ba1dfde (diff)
Revert "userfaultfd: don't fail on unrecognized features"
This is a proposal to revert commit 914eedcb9ba0ff53c33808. I found this when writing a simple UFFDIO_API test to be the first unit test in this set. Two things breaks with the commit: - UFFDIO_API check was lost and missing. According to man page, the kernel should reject ioctl(UFFDIO_API) if uffdio_api.api != 0xaa. This check is needed if the api version will be extended in the future, or user app won't be able to identify which is a new kernel. - Feature flags checks were removed, which means UFFDIO_API with a feature that does not exist will also succeed. According to the man page, we should (and it makes sense) to reject ioctl(UFFDIO_API) if unknown features passed in. Link: https://lore.kernel.org/r/20220722201513.1624158-1-axelrasmussen@google.com Link: https://lkml.kernel.org/r/20230412163922.327282-2-peterx@redhat.com Fixes: 914eedcb9ba0 ("userfaultfd: don't fail on unrecognized features") Signed-off-by: Peter Xu <peterx@redhat.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Zach O'Keefe <zokeefe@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--fs/userfaultfd.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 44d1ee429eb0..40f9e1a2ebdd 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1955,8 +1955,10 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
ret = -EFAULT;
if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
goto out;
- /* Ignore unsupported features (userspace built against newer kernel) */
- features = uffdio_api.features & UFFD_API_FEATURES;
+ features = uffdio_api.features;
+ ret = -EINVAL;
+ if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES))
+ goto err_out;
ret = -EPERM;
if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE))
goto err_out;