diff options
| -rw-r--r-- | include/linux/shmem_fs.h | 17 | ||||
| -rw-r--r-- | mm/shmem.c | 11 |
2 files changed, 28 insertions, 0 deletions
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index 650874b400b5..d34a64eafe60 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -24,6 +24,14 @@ struct swap_iocb; #define SHMEM_F_NORESERVE BIT(0) /* Disallow swapping. */ #define SHMEM_F_LOCKED BIT(1) +/* + * Disallow growing, shrinking, or hole punching in the inode. Combined with + * folio pinning, makes sure the inode's mapping stays fixed. + * + * In some ways similar to F_SEAL_GROW | F_SEAL_SHRINK, but can be removed and + * isn't directly visible to userspace. + */ +#define SHMEM_F_MAPPING_FROZEN BIT(2) struct shmem_inode_info { spinlock_t lock; @@ -186,6 +194,15 @@ static inline bool shmem_file(struct file *file) return shmem_mapping(file->f_mapping); } +/* Must be called with inode lock taken exclusive. */ +static inline void shmem_freeze(struct inode *inode, bool freeze) +{ + if (freeze) + SHMEM_I(inode)->flags |= SHMEM_F_MAPPING_FROZEN; + else + SHMEM_I(inode)->flags &= ~SHMEM_F_MAPPING_FROZEN; +} + /* * If fallocate(FALLOC_FL_KEEP_SIZE) has been used, there may be pages * beyond i_size's notion of EOF, which fallocate has committed to reserving: diff --git a/mm/shmem.c b/mm/shmem.c index 1d5036dec08a..786573479360 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1297,6 +1297,8 @@ static int shmem_setattr(struct mnt_idmap *idmap, return -EPERM; if (newsize != oldsize) { + if (info->flags & SHMEM_F_MAPPING_FROZEN) + return -EPERM; error = shmem_reacct_size(SHMEM_I(inode)->flags, oldsize, newsize); if (error) @@ -3289,6 +3291,10 @@ shmem_write_begin(const struct kiocb *iocb, struct address_space *mapping, return -EPERM; } + if (unlikely((info->flags & SHMEM_F_MAPPING_FROZEN) && + pos + len > inode->i_size)) + return -EPERM; + ret = shmem_get_folio(inode, index, pos + len, &folio, SGP_WRITE); if (ret) return ret; @@ -3662,6 +3668,11 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, inode_lock(inode); + if (info->flags & SHMEM_F_MAPPING_FROZEN) { + error = -EPERM; + goto out; + } + if (mode & FALLOC_FL_PUNCH_HOLE) { struct address_space *mapping = file->f_mapping; loff_t unmap_start = round_up(offset, PAGE_SIZE); |