f2fs: disallow mmap write and data-modifying fallocate on atomic files

Stores through a shared writable mapping and fallocate with
FALLOC_FL_PUNCH_HOLE, FALLOC_FL_ZERO_RANGE, FALLOC_FL_COLLAPSE_RANGE or
FALLOC_FL_INSERT_RANGE do not go through ->write_begin, so they bypass
the COW inode and modify the original inode directly. Reject them while
the file is in atomic write mode, as fallocate already does for pinned
and compressed files. A write fault gets SIGBUS and fallocate gets
-EOPNOTSUPP.

fallocate without these flags only preallocates blocks and stays
allowed.

f2fs_vm_page_mkwrite() cannot take inode_lock, so check the flag under
invalidate_lock, and hold invalidate_lock in
f2fs_ioc_start_atomic_write() from the flush until the flag is set.
Otherwise a fault could check the flag, then start_atomic_write could
flush and set the flag, and the fault would dirty the folio afterwards.

Cc: stable@kernel.org
Fixes: 3db1de0e582c ("f2fs: change the current atomic write way")
Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

0 files changed, 0 insertions, 0 deletions