linux-kernel - [PATCH] ntfs3: change to non-blocking allocation in ntfs_d

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Message-ID: <20240902171945.79656-1-djahchankoike@gmail.com>
Date: Mon,  2 Sep 2024 14:19:32 -0300
From: Diogo Jahchan Koike <djahchankoike@...il.com>
To: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
Cc: Diogo Jahchan Koike <djahchankoike@...il.com>,
	syzbot+7f71f79bbfb4427b00e1@...kaller.appspotmail.com,
	ntfs3@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH] ntfs3: change to non-blocking allocation in ntfs_d_hash

d_hash is done while under "rcu-walk" and should not sleep.
__get_name() allocates using GFP_KERNEL, having the possibility
to sleep when under memory pressure. Change the allocation to
GFP_NOWAIT.

Reported-by: syzbot+7f71f79bbfb4427b00e1@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7f71f79bbfb4427b00e1
Fixes: d392e85fd1e8 ("fs/ntfs3: Fix the format of the "nocase" mount option")
Signed-off-by: Diogo Jahchan Koike <djahchankoike@...il.com>
---
 fs/ntfs3/namei.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs3/namei.c b/fs/ntfs3/namei.c
index f16d318c4372..0a70c3658546 100644
--- a/fs/ntfs3/namei.c
+++ b/fs/ntfs3/namei.c
@@ -395,7 +395,7 @@ static int ntfs_d_hash(const struct dentry *dentry, struct qstr *name)
 	/*
 	 * Try slow way with current upcase table
 	 */
-	uni = __getname();
+	uni = kmem_cache_alloc(names_cachep, GFP_NOWAIT);
 	if (!uni)
 		return -ENOMEM;
 
@@ -417,7 +417,7 @@ static int ntfs_d_hash(const struct dentry *dentry, struct qstr *name)
 	err = 0;
 
 out:
-	__putname(uni);
+	kmem_cache_free(names_cachep, uni);
 	return err;
 }
 
-- 
2.43.0