linux-kernel - [PATCH] proc: use kmalloc instead of __get_free

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Message-ID: <20220123100837.GA1491@haolee.io>
Date:   Sun, 23 Jan 2022 10:08:37 +0000
From:   Hao Lee <haolee.swjtu@...il.com>
To:     akpm@...ux-foundation.org
Cc:     christian.brauner@...ntu.com, keescook@...omium.org,
        adobriyan@...il.com, jamorris@...ux.microsoft.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        haolee.swjtu@...il.com
Subject: [PATCH] proc: use kmalloc instead of __get_free_page() to alloc path
 buffer

It's not a standard approach that use __get_free_page() to alloc path
buffer directly. We'd better use kmalloc and PATH_MAX.

Signed-off-by: Hao Lee <haolee.swjtu@...il.com>
---
 fs/proc/base.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index d654ce7150fd..74cfef87fe45 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1764,25 +1764,26 @@ static const char *proc_pid_get_link(struct dentry *dentry,
 
 static int do_proc_readlink(struct path *path, char __user *buffer, int buflen)
 {
-	char *tmp = (char *)__get_free_page(GFP_KERNEL);
+	char *buf = NULL;
 	char *pathname;
 	int len;
 
-	if (!tmp)
+	buf = kmalloc(PATH_MAX, GFP_KERNEL);
+	if (!buf)
 		return -ENOMEM;
 
-	pathname = d_path(path, tmp, PAGE_SIZE);
+	pathname = d_path(path, buf, PATH_MAX);
 	len = PTR_ERR(pathname);
 	if (IS_ERR(pathname))
 		goto out;
-	len = tmp + PAGE_SIZE - 1 - pathname;
+	len = buf + PATH_MAX - 1 - pathname;
 
 	if (len > buflen)
 		len = buflen;
 	if (copy_to_user(buffer, pathname, len))
 		len = -EFAULT;
  out:
-	free_page((unsigned long)tmp);
+	kfree(buf);
 	return len;
 }
 
-- 
2.34.1