[PATCH 6.0 088/148] fs/ntfs3: dont hold ni_lock when calling truncate_setsize()

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From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>

[ Upstream commit 0226635c304cfd5c9db9b78c259cb713819b057e ]

syzbot is reporting hung task at do_user_addr_fault() [1], for there is
a silent deadlock between PG_locked bit and ni_lock lock.

Since filemap_update_page() calls filemap_read_folio() after calling
folio_trylock() which will set PG_locked bit, ntfs_truncate() must not
call truncate_setsize() which will wait for PG_locked bit to be cleared
when holding ni_lock lock.

Link: https://lore.kernel.org/all/00000000000060d41f05f139aa44@xxxxxxxxxx/
Link: https://syzkaller.appspot.com/bug?extid=bed15dbf10294aa4f2ae [1]
Reported-by: syzbot <syzbot+bed15dbf10294aa4f2ae@xxxxxxxxxxxxxxxxxxxxxxxxx>
Debugged-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Co-developed-by: Hillf Danton <hdanton@xxxxxxxx>
Signed-off-by: Hillf Danton <hdanton@xxxxxxxx>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Fixes: 4342306f0f0d ("fs/ntfs3: Add file operations and implementation")
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/ntfs3/file.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
index 4f2ffc7ef296..f31c0389a2e7 100644
--- a/fs/ntfs3/file.c
+++ b/fs/ntfs3/file.c
@@ -486,10 +486,10 @@ static int ntfs_truncate(struct inode *inode, loff_t new_size)
 
 	new_valid = ntfs_up_block(sb, min_t(u64, ni->i_valid, new_size));
 
-	ni_lock(ni);
-
 	truncate_setsize(inode, new_size);
 
+	ni_lock(ni);
+
 	down_write(&ni->file.run_lock);
 	err = attr_set_size(ni, ATTR_DATA, NULL, 0, &ni->file.run, new_size,
 			    &new_valid, ni->mi.sbi->options->prealloc, NULL);
-- 
2.35.1






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