[Ocfs2-devel] [PATCH] ocfs2: no need try to truncate file beyond i_size

[Changwei Ge]

Linux fallocate(2) with FALLOC_FL_PUNCH_HOLE mode set, its offset can
exceed inode size. Ocfs2 now does't allow that offset beyond inode size.
This restriction is not necessary and voilates fallocate(2) semantics.

If fallocate(2) offset is beyond inode size, just return success and do
nothing further.

Otherwise, ocfs2 will crash the kernel.

---
kernel BUG at fs/ocfs2//alloc.c:7264!
 ocfs2_truncate_inline+0x20f/0x360 [ocfs2]
 ? ocfs2_read_blocks+0x2f3/0x5f0 [ocfs2]
 ocfs2_remove_inode_range+0x23c/0xcb0 [ocfs2]
 ? ocfs2_read_inode_block+0x10/0x20 [ocfs2]
 ? ocfs2_allocate_extend_trans+0x1a0/0x1a0 [ocfs2]
 __ocfs2_change_file_space+0x4a5/0x650 [ocfs2]
 ocfs2_fallocate+0x83/0xa0 [ocfs2]
 ? __audit_syscall_entry+0xb8/0x100
 ? __sb_start_write+0x3b/0x70
 vfs_fallocate+0x148/0x230
 SyS_fallocate+0x48/0x80
 do_syscall_64+0x79/0x170

Signed-off-by: Changwei Ge <chge at linux.alibaba.com>
Cc: <stable at vger.kernel.org>
---
 fs/ocfs2/alloc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index 88534eb0e7c..3d5b6b989db 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -7403,6 +7403,10 @@ int ocfs2_truncate_inline(struct inode *inode, struct buffer_head *di_bh,
 	struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
 	struct ocfs2_inline_data *idata = &di->id2.i_data;
 
+	/* No need to punch hole beyond i_size. */
+	if (start >= i_size_read(inode))
+		return 0;
+
 	if (end > i_size_read(inode))
 		end = i_size_read(inode);
 
-- 
2.17.1