diff options
| author | Ondrej Mosnacek <[email protected]> | 2022-07-08 11:34:51 +0200 |
|---|---|---|
| committer | Paul Moore <[email protected]> | 2022-08-30 16:04:31 -0400 |
| commit | abec3d015fdfb7c63105c7e1c956188bf381aa55 (patch) | |
| tree | 0b08d9667430f799571ac6ffaef6c04210c8e873 | |
| parent | ed5d44d42c95e8a13bb54e614d2269c8740667f9 (diff) | |
userfaultfd: open userfaultfds with O_RDONLY
Since userfaultfd doesn't implement a write operation, it is more
appropriate to open it read-only.
When userfaultfds are opened read-write like it is now, and such fd is
passed from one process to another, SELinux will check both read and
write permissions for the target process, even though it can't actually
do any write operation on the fd later.
Inspired by the following bug report, which has hit the SELinux scenario
described above:
https://bugzilla.redhat.com/show_bug.cgi?id=1974559
Reported-by: Robert O'Callahan <[email protected]>
Fixes: 86039bd3b4e6 ("userfaultfd: add new syscall to provide memory externalization")
Signed-off-by: Ondrej Mosnacek <[email protected]>
Acked-by: Peter Xu <[email protected]>
Acked-by: Christian Brauner (Microsoft) <[email protected]>
Signed-off-by: Paul Moore <[email protected]>
| -rw-r--r-- | fs/userfaultfd.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 1c44bf75f916..e6ffe7bc59e3 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -991,7 +991,7 @@ static int resolve_userfault_fork(struct userfaultfd_ctx *new, int fd; fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, new, - O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode); + O_RDONLY | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode); if (fd < 0) return fd; @@ -2090,7 +2090,7 @@ SYSCALL_DEFINE1(userfaultfd, int, flags) mmgrab(ctx->mm); fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, ctx, - O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL); + O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL); if (fd < 0) { mmdrop(ctx->mm); kmem_cache_free(userfaultfd_ctx_cachep, ctx); |