[Devel] [PATCH vz10] hugetlbfs: enforce F_SEAL_EXEC in setattr

[Konstantin Khorenko]

On 6/25/26 00:38, Eva Kurchatova wrote:
> Commit 6fd735518263 ('mm/memfd: add F_SEAL_EXEC') added the F_SEAL_EXEC
> seal to memfd, with the corresponding enforcement implemented in
> shmem_setattr(): once F_SEAL_EXEC is set, fchmod() of any of the execute
> bits (S_IXUSR|S_IXGRP|S_IXOTH) is rejected with -EPERM.
> 
> The hugetlbfs equivalent in hugetlbfs_setattr() was missed, even though
> hugetlbfs memfd files carry the same 'info->seals' bitmap and the same
> F_SEAL_EXEC bit can be added through memfd_create(... MFD_HUGETLB ...)
> plus fcntl(F_ADD_SEALS, F_SEAL_EXEC). As a result, the seal is silently
> ignored on hugetlbfs memfds and fchmod() may turn execute bits back on
> after the seal has been applied.
> 
> Mirror the shmem check in hugetlbfs_setattr() so that ATTR_MODE changes
> that flip any execute bit on a sealed inode return -EPERM. This also
> fixes the memfd_test 'hugetlbfs' SEAL-EXEC subtest, which previously
> aborted on:
> 
>     fchmod(/memfd:kern_memfd_seal_exec (deleted), 00777) didn't fail as expected
> 
> Fixes: 6fd735518263 ("mm/memfd: add F_SEAL_EXEC")

Wrong git commit id. The correct one is:
6fd7353829caf mm/memfd: add F_SEAL_EXEC

> Signed-off-by: Eva Kurchatova <eva.kurchatova at virtuozzo.com>
> 
> https://virtuozzo.atlassian.net/browse/VSTOR-133571
> Feature: fix selftests
> 
> ---
>  fs/hugetlbfs/inode.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 5cf327337e22..1e5cffded6a5 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -935,6 +935,11 @@ static int hugetlbfs_setattr(struct mnt_idmap *idmap,
>  	if (error)
>  		return error;
>  
> +	if ((info->seals & F_SEAL_EXEC) && (ia_valid & ATTR_MODE)) {
> +		if ((inode->i_mode ^ attr->ia_mode) & 0111)
> +			return -EPERM;
> +	}
> +
>  	if (ia_valid & ATTR_SIZE) {
>  		loff_t oldsize = inode->i_size;
>  		loff_t newsize = attr->ia_size;