6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daeho Jeong [ Upstream commit 06dfe4a7eb696d868b196c2a49873142f19bd862 ] 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 Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim Signed-off-by: Sasha Levin --- fs/f2fs/file.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 86f1f734caaac..8211ee75fb8f7 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -177,6 +177,17 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf) file_update_time(vmf->vma->vm_file); filemap_invalidate_lock_shared(inode->i_mapping); + /* + * mmap stores bypass the COW inode and would break atomicity. Check + * under invalidate_lock: f2fs_ioc_start_atomic_write() holds it while + * flushing dirty folios and setting FI_ATOMIC_FILE, so either it sees + * our dirty folio and writes it back, or we see the flag. + */ + if (unlikely(f2fs_is_atomic_file(inode))) { + err = -EOPNOTSUPP; + goto out_sem; + } + folio_lock(folio); /* * A concurrent buffered write can extend isize, so we store isize in a @@ -2081,9 +2092,11 @@ static long f2fs_fallocate(struct file *file, int mode, /* * Pinned file should not support partial truncation since the block - * can be used by applications. + * can be used by applications. Atomic files should not either, since + * these modify the original inode directly and break atomicity. */ - if ((f2fs_compressed_file(inode) || f2fs_is_pinned_file(inode)) && + if ((f2fs_compressed_file(inode) || f2fs_is_pinned_file(inode) || + f2fs_is_atomic_file(inode)) && (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE | FALLOC_FL_INSERT_RANGE))) { ret = -EOPNOTSUPP; @@ -2368,6 +2381,8 @@ static int f2fs_ioc_start_atomic_write(struct file *filp, bool truncate) f2fs_down_write(&fi->i_gc_rwsem[WRITE]); f2fs_down_write(&fi->i_gc_rwsem[READ]); + /* serialize with f2fs_vm_page_mkwrite(), see the comment there */ + filemap_invalidate_lock(inode->i_mapping); /* * Should wait end_io to count F2FS_WB_CP_DATA correctly by @@ -2423,6 +2438,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp, bool truncate) f2fs_i_size_write(fi->cow_inode, isize); out_unlock: + filemap_invalidate_unlock(inode->i_mapping); f2fs_up_write(&fi->i_gc_rwsem[READ]); f2fs_up_write(&fi->i_gc_rwsem[WRITE]); if (ret) -- 2.53.0