5.4-stable review patch. If anyone has any objections, please let me know.
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From: Lorenzo Stoakes lstoakes@gmail.com
[ Upstream commit 28464bbb2ddc199433383994bcb9600c8034afa1 ]
The seal_check_future_write() function is called by shmem_mmap() or hugetlbfs_file_mmap() to disallow any future writable mappings of an memfd sealed this way.
The F_SEAL_WRITE flag is not checked here, as that is handled via the mapping->i_mmap_writable mechanism and so any attempt at a mapping would fail before this could be run.
However we intend to change this, meaning this check can be performed for F_SEAL_WRITE mappings also.
The logic here is equally applicable to both flags, so update this function to accommodate both and rename it accordingly.
Link: https://lkml.kernel.org/r/913628168ce6cce77df7d13a63970bae06a526e0.169711658... Signed-off-by: Lorenzo Stoakes lstoakes@gmail.com Reviewed-by: Jan Kara jack@suse.cz Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: Andy Lutomirski luto@kernel.org Cc: Christian Brauner brauner@kernel.org Cc: Hugh Dickins hughd@google.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Mike Kravetz mike.kravetz@oracle.com Cc: Muchun Song muchun.song@linux.dev Signed-off-by: Andrew Morton akpm@linux-foundation.org Cc: stable@vger.kernel.org Signed-off-by: Isaac J. Manjarres isaacmanjarres@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/hugetlbfs/inode.c | 2 +- include/linux/mm.h | 15 ++++++++------- mm/shmem.c | 2 +- 3 files changed, 10 insertions(+), 9 deletions(-)
--- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -152,7 +152,7 @@ static int hugetlbfs_file_mmap(struct fi vma->vm_flags |= VM_HUGETLB | VM_DONTEXPAND; vma->vm_ops = &hugetlb_vm_ops;
- ret = seal_check_future_write(info->seals, vma); + ret = seal_check_write(info->seals, vma); if (ret) return ret;
--- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2946,25 +2946,26 @@ static inline int pages_identical(struct }
/** - * seal_check_future_write - Check for F_SEAL_FUTURE_WRITE flag and handle it + * seal_check_write - Check for F_SEAL_WRITE or F_SEAL_FUTURE_WRITE flags and + * handle them. * @seals: the seals to check * @vma: the vma to operate on * - * Check whether F_SEAL_FUTURE_WRITE is set; if so, do proper check/handling on - * the vma flags. Return 0 if check pass, or <0 for errors. + * Check whether F_SEAL_WRITE or F_SEAL_FUTURE_WRITE are set; if so, do proper + * check/handling on the vma flags. Return 0 if check pass, or <0 for errors. */ -static inline int seal_check_future_write(int seals, struct vm_area_struct *vma) +static inline int seal_check_write(int seals, struct vm_area_struct *vma) { - if (seals & F_SEAL_FUTURE_WRITE) { + if (seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) { /* * New PROT_WRITE and MAP_SHARED mmaps are not allowed when - * "future write" seal active. + * write seals are 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 + * 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 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2215,7 +2215,7 @@ static int shmem_mmap(struct file *file, struct shmem_inode_info *info = SHMEM_I(file_inode(file)); int ret;
- ret = seal_check_future_write(info->seals, vma); + ret = seal_check_write(info->seals, vma); if (ret) return ret;