Ocfs2 devel - Apr 2020 - [PATCH AUTOSEL 4.9 18/23] ocfs2: no need try to truncate file beyond i_size

From: Changwei Ge <chge at linux.alibaba.com>

[ Upstream commit 783fda856e1034dee90a873f7654c418212d12d7 ]

Linux fallocate(2) with FALLOC_FL_PUNCH_HOLE mode set, its offset can
exceed the inode size.  Ocfs2 now doesn't allow that offset beyond inode
size.  This restriction is not necessary and violates 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_remove_inode_range+0x23c/0xcb0 [ocfs2]
   __ocfs2_change_file_space+0x4a5/0x650 [ocfs2]
   ocfs2_fallocate+0x83/0xa0 [ocfs2]
   vfs_fallocate+0x148/0x230
   SyS_fallocate+0x48/0x80
   do_syscall_64+0x79/0x170

Signed-off-by: Changwei Ge <chge at linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Reviewed-by: Joseph Qi <joseph.qi at linux.alibaba.com>
Cc: Mark Fasheh <mark at fasheh.com>
Cc: Joel Becker <jlbec at evilplan.org>
Cc: Junxiao Bi <junxiao.bi at oracle.com>
Cc: Changwei Ge <gechangwei at live.cn>
Cc: Gang He <ghe at suse.com>
Cc: Jun Piao <piaojun at huawei.com>
Cc: <stable at vger.kernel.org>
Link:
https://urldefense.com/v3/__http://lkml.kernel.org/r/20200407082754.17565-1-chge
at
linux.alibaba.com__;!!GqivPVa7Brio!LUrD352okiIdCwv4iKGw97iYKybbPF1-QjfRg5fG-SokF5WyTtdqcd3OvwvG0URGXuFPNg$
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Sasha Levin <sashal at 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 06089becca607..dfb8a923921e0 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -7246,6 +7246,10 @@ 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);
 
-- 
2.20.1