linux-kernel - [PATCH] locks: avoid usage of list iterator after loop in generic_delete

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Date:   Wed, 01 Mar 2023 18:20:18 +0100
From:   Jakob Koschel <jkl820.git@...il.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Jeff Layton <jlayton@...nel.org>,
        Chuck Lever <chuck.lever@...cle.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pietro Borrello <borrello@...g.uniroma1.it>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>, Jakob Koschel <jkl820.git@...il.com>
Subject: [PATCH] locks: avoid usage of list iterator after loop in
 generic_delete_lease()

'victim' and 'fl' are ensured to be equal at this point. For consistency
both should use the same variable.

Additionally, Linus proposed to avoid any use of the list iterator
variable after the loop, in the attempt to move the list iterator
variable declaration into the marcro to avoid any potential misuse after
the loop [1].

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <jkl820.git@...il.com>
---
 fs/locks.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/locks.c b/fs/locks.c
index 66b4eef09db5..3f46d21a95f4 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1841,7 +1841,7 @@ static int generic_delete_lease(struct file *filp, void *owner)
 	}
 	trace_generic_delete_lease(inode, victim);
 	if (victim)
-		error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
+		error = victim->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
 	spin_unlock(&ctx->flc_lock);
 	percpu_up_read(&file_rwsem);
 	locks_dispose_list(&dispose);

---
base-commit: c0927a7a5391f7d8e593e5e50ead7505a23cadf9
change-id: 20230301-locks-avoid-iter-after-loop-0c6cc0fbd295

Best regards,
-- 
Jakob Koschel <jkl820.git@...il.com>