F2FS large folio support is read-only. It rejects writable opens and
mmap writes when an inode mapping supports large folios, but setattr can
still reach the inode without going through those checks.
For immutable large-folio files, clearing the immutable flag keeps the
cached inode and its large-folio mapping alive until the inode is
dropped. A path-based truncate(2) can then call f2fs_setattr() with
ATTR_SIZE and change the file size without opening the file for write.
The user.fadvise path adds another visible case: after the file is
reopened with large folios, chmod(WRITE) is documented to fail, but
f2fs_setattr() currently allows ATTR_MODE to add write bits back.
Reject size changes and mode changes that enable write permissions while
the mapping still supports large folios. Read-only mode changes and
unrelated metadata updates remain allowed.
Fixes: 05e65c14ea59 ("f2fs: support large folio for immutable non-compressed
case")
Signed-off-by: Wenjie Qi <[email protected]>
---
fs/f2fs/file.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 71385ca4163d..3880ff5e6740 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1097,6 +1097,11 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry
*dentry,
ATTR_GID | ATTR_TIMES_SET))))
return -EPERM;
+ if (mapping_large_folio_support(inode->i_mapping) &&
+ ((attr->ia_valid & ATTR_SIZE) ||
+ ((attr->ia_valid & ATTR_MODE) && (attr->ia_mode & 0222))))
+ return -EOPNOTSUPP;
+
if ((attr->ia_valid & ATTR_SIZE)) {
if (!f2fs_is_compress_backend_ready(inode) ||
IS_DEVICE_ALIASING(inode))
--
2.43.0
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