| Message ID | 913628168ce6cce77df7d13a63970bae06a526e0.1697116581.git.lstoakes@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | permit write-sealed memfd read-only shared mappings | expand |
On Thu 12-10-23 18:04:29, Lorenzo Stoakes wrote: > 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. > > Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com> For some reason only this one patch landed in my inbox but I've checked all three on lore and they look good to me. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> to all of them. Thanks! Honza > --- > fs/hugetlbfs/inode.c | 2 +- > include/linux/mm.h | 15 ++++++++------- > mm/shmem.c | 2 +- > 3 files changed, 10 insertions(+), 9 deletions(-) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index 06693bb1153d..5c333373dcc9 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -112,7 +112,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) > vm_flags_set(vma, 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; > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index bae234d18d81..26d7dc3b342b 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -4078,25 +4078,26 @@ static inline void mem_dump_obj(void *object) {} > #endif > > /** > - * 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 > diff --git a/mm/shmem.c b/mm/shmem.c > index 6503910b0f54..cab053831fea 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2405,7 +2405,7 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma) > struct shmem_inode_info *info = SHMEM_I(inode); > int ret; > > - ret = seal_check_future_write(info->seals, vma); > + ret = seal_check_write(info->seals, vma); > if (ret) > return ret; > > -- > 2.42.0 >
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 06693bb1153d..5c333373dcc9 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -112,7 +112,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) vm_flags_set(vma, 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; diff --git a/include/linux/mm.h b/include/linux/mm.h index bae234d18d81..26d7dc3b342b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -4078,25 +4078,26 @@ static inline void mem_dump_obj(void *object) {} #endif /** - * 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 diff --git a/mm/shmem.c b/mm/shmem.c index 6503910b0f54..cab053831fea 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2405,7 +2405,7 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma) struct shmem_inode_info *info = SHMEM_I(inode); int ret; - ret = seal_check_future_write(info->seals, vma); + ret = seal_check_write(info->seals, vma); if (ret) return ret;
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. Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com> --- fs/hugetlbfs/inode.c | 2 +- include/linux/mm.h | 15 ++++++++------- mm/shmem.c | 2 +- 3 files changed, 10 insertions(+), 9 deletions(-)