linux-kernel - [RFC PATCH 09/27] reverse_path_check

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Message-Id: <20201004023929.2740074-9-viro@ZenIV.linux.org.uk>
Date:   Sun,  4 Oct 2020 03:39:11 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>
Subject: [RFC PATCH 09/27] reverse_path_check_proc(): don't bother with cookies

From: Al Viro <viro@...iv.linux.org.uk>

We know there's no loops by the time we call it; the
only thing we care about is too deep reverse paths.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/eventpoll.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 3e6f1f97f246..0f540e91aa92 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1311,7 +1311,7 @@ static int reverse_path_check_proc(struct file *file, int depth)
 	int error = 0;
 	struct epitem *epi;
 
-	if (!ep_push_nested(file)) /* limits recursion */
+	if (depth > EP_MAX_NESTS) /* too deep nesting */
 		return -1;
 
 	/* CTL_DEL can remove links here, but that can't increase our count */
@@ -1336,7 +1336,6 @@ static int reverse_path_check_proc(struct file *file, int depth)
 		}
 	}
 	rcu_read_unlock();
-	nesting--; /* pop */
 	return error;
 }
 
-- 
2.11.0