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094e94d13b
Prior to this change, no security hooks were called at the creation of a memfd file. It means that, for SELinux as an example, it will receive the default type of the filesystem that backs the in-memory inode. In most cases, that would be tmpfs, but if MFD_HUGETLB is passed, it will be hugetlbfs. Both can be considered implementation details of memfd. It also means that it is not possible to differentiate between a file coming from memfd_create and a file coming from a standard tmpfs mount point. Additionally, no permission is validated at creation, which differs from the similar memfd_secret syscall. Call security_inode_init_security_anon during creation. This ensures that the file is setup similarly to other anonymous inodes. On SELinux, it means that the file will receive the security context of its task. The ability to limit fexecve on memfd has been of interest to avoid potential pitfalls where /proc/self/exe or similar would be executed [1][2]. Reuse the "execute_no_trans" and "entrypoint" access vectors, similarly to the file class. These access vectors may not make sense for the existing "anon_inode" class. Therefore, define and assign a new class "memfd_file" to support such access vectors. Guard these changes behind a new policy capability named "memfd_class". [1] https://crbug.com/1305267 [2] https://lore.kernel.org/lkml/20221215001205.51969-1-jeffxu@google.com/ Signed-off-by: Thiébaud Weksteen <tweek@google.com> Reviewed-by: Stephen Smalley <stephen.smalley.work@gmail.com> Tested-by: Stephen Smalley <stephen.smalley.work@gmail.com> Acked-by: Hugh Dickins <hughd@google.com> [PM: subj tweak] Signed-off-by: Paul Moore <paul@paul-moore.com>
37 lines
979 B
C
37 lines
979 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_MEMFD_H
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#define __LINUX_MEMFD_H
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#include <linux/file.h>
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#define MEMFD_ANON_NAME "[memfd]"
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#ifdef CONFIG_MEMFD_CREATE
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extern long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg);
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struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx);
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/*
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* Check for any existing seals on mmap, return an error if access is denied due
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* to sealing, or 0 otherwise.
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*
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* We also update VMA flags if appropriate by manipulating the VMA flags pointed
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* to by vm_flags_ptr.
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*/
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int memfd_check_seals_mmap(struct file *file, vm_flags_t *vm_flags_ptr);
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#else
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static inline long memfd_fcntl(struct file *f, unsigned int c, unsigned int a)
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{
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return -EINVAL;
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}
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static inline struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
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{
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return ERR_PTR(-EINVAL);
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}
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static inline int memfd_check_seals_mmap(struct file *file,
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vm_flags_t *vm_flags_ptr)
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{
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return 0;
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}
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#endif
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#endif /* __LINUX_MEMFD_H */
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